diff --git a/src/main/java/io/roastedroot/proxywasm/ABI.java b/src/main/java/io/roastedroot/proxywasm/ABI.java
index e8b48b5..cd8a762 100644
--- a/src/main/java/io/roastedroot/proxywasm/ABI.java
+++ b/src/main/java/io/roastedroot/proxywasm/ABI.java
@@ -12,7 +12,6 @@
 import com.dylibso.chicory.wasm.InvalidException;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
-import java.util.HashMap;
 import java.util.Map;
 
 @HostModule("env")
@@ -675,19 +674,18 @@ int proxyGetHeaderMapSize(int mapType, int returnSize) {
         try {
 
             // Get the header map based on the map type
-            Map<String, String> header = getMap(mapType);
+            ProxyMap header = getMap(mapType);
             if (header == null) {
                 return WasmResult.BAD_ARGUMENT.getValue();
             }
 
             // to clone the headers so that they don't change on while we process them in the loop
-            final Map<String, String> cloneMap = new HashMap<>();
+            var cloneMap = new ArrayProxyMap(header);
             int totalBytesLen = U32_LEN; // Start with space for the count
 
-            for (Map.Entry<String, String> entry : header.entrySet()) {
+            for (Map.Entry<String, String> entry : cloneMap.entries()) {
                 String key = entry.getKey();
                 String value = entry.getValue();
-                cloneMap.put(key, value);
                 totalBytesLen += U32_LEN + U32_LEN; // keyLen + valueLen
                 totalBytesLen += key.length() + 1 + value.length() + 1; // key + \0 + value + \0
             }
@@ -717,19 +715,18 @@ int proxyGetHeaderMapPairs(int mapType, int returnDataPtr, int returnDataSize) {
         try {
 
             // Get the header map based on the map type
-            Map<String, String> header = getMap(mapType);
+            ProxyMap header = getMap(mapType);
             if (header == null) {
                 return WasmResult.NOT_FOUND.getValue();
             }
 
             // to clone the headers so that they don't change on while we process them in the loop
-            final Map<String, String> cloneMap = new HashMap<>();
+            var cloneMap = new ArrayProxyMap(header);
             int totalBytesLen = U32_LEN; // Start with space for the count
 
-            for (Map.Entry<String, String> entry : header.entrySet()) {
+            for (Map.Entry<String, String> entry : cloneMap.entries()) {
                 String key = entry.getKey();
                 String value = entry.getValue();
-                cloneMap.put(key, value);
                 totalBytesLen += U32_LEN + U32_LEN; // keyLen + valueLen
                 totalBytesLen += key.length() + 1 + value.length() + 1; // key + \0 + value + \0
             }
@@ -745,7 +742,7 @@ int proxyGetHeaderMapPairs(int mapType, int returnDataPtr, int returnDataSize) {
             int dataPtr = lenPtr + ((U32_LEN + U32_LEN) * cloneMap.size());
 
             // Write each key-value pair to memory
-            for (Map.Entry<String, String> entry : cloneMap.entrySet()) {
+            for (Map.Entry<String, String> entry : cloneMap.entries()) {
                 String key = entry.getKey();
                 String value = entry.getValue();
 
@@ -802,14 +799,14 @@ int proxySetHeaderMapPairs(int mapType, int ptr, int size) {
 
         try {
             // Get the header map based on the map type
-            Map<String, String> headerMap = getMap(mapType);
+            ProxyMap headerMap = getMap(mapType);
             if (headerMap == null) {
                 return WasmResult.BAD_ARGUMENT.getValue();
             }
 
             // Decode the map content and set each key-value pair
-            Map<String, String> newMap = decodeMap(ptr, size);
-            for (Map.Entry<String, String> entry : newMap.entrySet()) {
+            ProxyMap newMap = decodeMap(ptr, size);
+            for (Map.Entry<String, String> entry : newMap.entries()) {
                 headerMap.put(entry.getKey(), entry.getValue());
             }
 
@@ -837,7 +834,7 @@ int proxyGetHeaderMapValue(
             int mapType, int keyDataPtr, int keySize, int valueDataPtr, int valueSize) {
         try {
             // Get the header map based on the map type
-            Map<String, String> headerMap = getMap(mapType);
+            ProxyMap headerMap = getMap(mapType);
             if (headerMap == null) {
                 return WasmResult.BAD_ARGUMENT.getValue();
             }
@@ -895,7 +892,7 @@ int proxyReplaceHeaderMapValue(
             int mapType, int keyDataPtr, int keySize, int valueDataPtr, int valueSize) {
         try {
             // Get the header map based on the map type
-            Map<String, String> headerMap = getMap(mapType);
+            ProxyMap headerMap = getMap(mapType);
             if (headerMap == null) {
                 return WasmResult.BAD_ARGUMENT.getValue();
             }
@@ -907,7 +904,7 @@ int proxyReplaceHeaderMapValue(
             String value = readString(valueDataPtr, valueSize);
 
             // Replace value in map
-            var copy = new HashMap<>(headerMap);
+            var copy = new ArrayProxyMap(headerMap);
             copy.put(key, value);
             setMap(mapType, copy);
 
@@ -933,7 +930,7 @@ int proxyReplaceHeaderMapValue(
     int proxyRemoveHeaderMapValue(int mapType, int keyDataPtr, int keySize) {
         try {
             // Get the header map based on the map type
-            Map<String, String> headerMap = getMap(mapType);
+            ProxyMap headerMap = getMap(mapType);
             if (headerMap == null) {
                 return WasmResult.NOT_FOUND.getValue();
             }
@@ -945,7 +942,7 @@ int proxyRemoveHeaderMapValue(int mapType, int keyDataPtr, int keySize) {
             }
 
             // Remove key from map
-            var copy = new HashMap<>(headerMap);
+            var copy = new ArrayProxyMap(headerMap);
             copy.remove(key);
             setMap(mapType, copy);
 
@@ -964,7 +961,7 @@ int proxyRemoveHeaderMapValue(int mapType, int keyDataPtr, int keySize) {
      * @param mapType The type of map to get
      * @return The header map
      */
-    private Map<String, String> getMap(int mapType) {
+    private ProxyMap getMap(int mapType) {
 
         var knownType = MapType.fromInt(mapType);
         if (knownType == null) {
@@ -999,7 +996,7 @@ private Map<String, String> getMap(int mapType) {
      * @param map     The header map to set
      * @return WasmResult indicating success or failure
      */
-    private WasmResult setMap(int mapType, Map<String, String> map) {
+    private WasmResult setMap(int mapType, ProxyMap map) {
         var knownType = MapType.fromInt(mapType);
         if (knownType == null) {
             return handler.setCustomHeaders(mapType, map);
@@ -1043,9 +1040,9 @@ private WasmResult setMap(int mapType, Map<String, String> map) {
      * @return The decoded map containing string keys and values
      * @throws WasmException if there is an error accessing memory
      */
-    private HashMap<String, String> decodeMap(int addr, int mem_size) throws WasmException {
+    private ProxyMap decodeMap(int addr, int mem_size) throws WasmException {
         if (mem_size < U32_LEN) {
-            return new HashMap<>();
+            return new ArrayProxyMap();
         }
 
         // Read header size (number of entries)
@@ -1055,11 +1052,11 @@ private HashMap<String, String> decodeMap(int addr, int mem_size) throws WasmExc
         // mapSize + (key1_size + value1_size) * mapSize
         long dataOffset = U32_LEN + (U32_LEN + U32_LEN) * mapSize;
         if (dataOffset >= mem_size) {
-            return new HashMap<>();
+            return new ArrayProxyMap();
         }
 
         // Create result map with initial capacity
-        var result = new HashMap<String, String>((int) mapSize);
+        var result = new ArrayProxyMap((int) mapSize);
 
         // Process each entry
         for (int i = 0; i < mapSize; i++) {
@@ -1086,7 +1083,7 @@ private HashMap<String, String> decodeMap(int addr, int mem_size) throws WasmExc
             dataOffset += valueSize + 1;
 
             // Add to result map
-            result.put(key, value);
+            result.add(key, value);
         }
 
         return result;
@@ -1282,8 +1279,7 @@ int proxySendLocalResponse(
             }
 
             // Get and decode additional headers from memory
-            HashMap<String, String> additionalHeaders =
-                    decodeMap(additionalHeadersMapData, additionalHeadersSize);
+            ProxyMap additionalHeaders = decodeMap(additionalHeadersMapData, additionalHeadersSize);
 
             // Send the response through the handler
             WasmResult result =
diff --git a/src/main/java/io/roastedroot/proxywasm/ArrayProxyMap.java b/src/main/java/io/roastedroot/proxywasm/ArrayProxyMap.java
new file mode 100644
index 0000000..a98db45
--- /dev/null
+++ b/src/main/java/io/roastedroot/proxywasm/ArrayProxyMap.java
@@ -0,0 +1,86 @@
+package io.roastedroot.proxywasm;
+
+import java.util.ArrayList;
+import java.util.Map;
+import java.util.Objects;
+
+public class ArrayProxyMap implements ProxyMap {
+
+    final ArrayList<Map.Entry<String, String>> entries;
+
+    public ArrayProxyMap() {
+        this.entries = new ArrayList<>();
+    }
+
+    public ArrayProxyMap(int mapSize) {
+        this.entries = new ArrayList<>(mapSize);
+    }
+
+    public ArrayProxyMap(ProxyMap other) {
+        this(other.size());
+        for (Map.Entry<String, String> entry : other.entries()) {
+            add(entry.getKey(), entry.getValue());
+        }
+    }
+
+    public ArrayProxyMap(Map<String, String> other) {
+        this(other.size());
+        for (Map.Entry<String, String> entry : other.entrySet()) {
+            add(entry.getKey(), entry.getValue());
+        }
+    }
+
+    @Override
+    public int size() {
+        return entries.size();
+    }
+
+    @Override
+    public void add(String key, String value) {
+        entries.add(Map.entry(key, value));
+    }
+
+    @Override
+    public void put(String key, String value) {
+        this.remove(key);
+        entries.add(Map.entry(key, value));
+    }
+
+    @Override
+    public Iterable<? extends Map.Entry<String, String>> entries() {
+        return entries;
+    }
+
+    @Override
+    public String get(String key) {
+        return entries.stream()
+                .filter(x -> x.getKey().equals(key))
+                .map(Map.Entry::getValue)
+                .findFirst()
+                .orElse(null);
+    }
+
+    @Override
+    public void remove(String key) {
+        entries.removeIf(x -> x.getKey().equals(key));
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        ArrayProxyMap that = (ArrayProxyMap) o;
+        return Objects.equals(entries, that.entries);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(entries);
+    }
+
+    @Override
+    public String toString() {
+        return entries.toString();
+    }
+}
diff --git a/src/main/java/io/roastedroot/proxywasm/ChainedHandler.java b/src/main/java/io/roastedroot/proxywasm/ChainedHandler.java
index 55ec17b..23b13aa 100644
--- a/src/main/java/io/roastedroot/proxywasm/ChainedHandler.java
+++ b/src/main/java/io/roastedroot/proxywasm/ChainedHandler.java
@@ -1,8 +1,5 @@
 package io.roastedroot.proxywasm;
 
-import java.util.HashMap;
-import java.util.Map;
-
 /**
  * A Handler implementation that chains to another handler if it can't handle the request.
  */
@@ -16,92 +13,92 @@ public void log(LogLevel level, String message) throws WasmException {
     }
 
     @Override
-    public Map<String, String> getHttpRequestHeaders() {
+    public ProxyMap getHttpRequestHeaders() {
         return next().getHttpRequestHeaders();
     }
 
     @Override
-    public Map<String, String> getHttpRequestTrailers() {
+    public ProxyMap getHttpRequestTrailers() {
         return next().getHttpRequestTrailers();
     }
 
     @Override
-    public Map<String, String> getHttpResponseHeaders() {
+    public ProxyMap getHttpResponseHeaders() {
         return next().getHttpResponseHeaders();
     }
 
     @Override
-    public Map<String, String> getHttpResponseTrailers() {
+    public ProxyMap getHttpResponseTrailers() {
         return next().getHttpResponseTrailers();
     }
 
     @Override
-    public Map<String, String> getHttpCallResponseHeaders() {
+    public ProxyMap getHttpCallResponseHeaders() {
         return next().getHttpCallResponseHeaders();
     }
 
     @Override
-    public Map<String, String> getHttpCallResponseTrailers() {
+    public ProxyMap getHttpCallResponseTrailers() {
         return next().getHttpCallResponseTrailers();
     }
 
     @Override
-    public Map<String, String> getGrpcReceiveInitialMetaData() {
+    public ProxyMap getGrpcReceiveInitialMetaData() {
         return next().getGrpcReceiveInitialMetaData();
     }
 
     @Override
-    public Map<String, String> getGrpcReceiveTrailerMetaData() {
+    public ProxyMap getGrpcReceiveTrailerMetaData() {
         return next().getGrpcReceiveTrailerMetaData();
     }
 
     @Override
-    public Map<String, String> getCustomHeaders(int mapType) {
+    public ProxyMap getCustomHeaders(int mapType) {
         return next().getCustomHeaders(mapType);
     }
 
     @Override
-    public WasmResult setCustomHeaders(int mapType, Map<String, String> map) {
+    public WasmResult setCustomHeaders(int mapType, ProxyMap map) {
         return next().setCustomHeaders(mapType, map);
     }
 
     @Override
-    public WasmResult setHttpRequestHeaders(Map<String, String> headers) {
+    public WasmResult setHttpRequestHeaders(ProxyMap headers) {
         return next().setHttpRequestHeaders(headers);
     }
 
     @Override
-    public WasmResult setHttpRequestTrailers(Map<String, String> trailers) {
+    public WasmResult setHttpRequestTrailers(ProxyMap trailers) {
         return next().setHttpRequestTrailers(trailers);
     }
 
     @Override
-    public WasmResult setHttpResponseHeaders(Map<String, String> headers) {
+    public WasmResult setHttpResponseHeaders(ProxyMap headers) {
         return next().setHttpResponseHeaders(headers);
     }
 
     @Override
-    public WasmResult setHttpResponseTrailers(Map<String, String> trailers) {
+    public WasmResult setHttpResponseTrailers(ProxyMap trailers) {
         return next().setHttpResponseTrailers(trailers);
     }
 
     @Override
-    public WasmResult setHttpCallResponseHeaders(Map<String, String> headers) {
+    public WasmResult setHttpCallResponseHeaders(ProxyMap headers) {
         return next().setHttpCallResponseHeaders(headers);
     }
 
     @Override
-    public WasmResult setHttpCallResponseTrailers(Map<String, String> trailers) {
+    public WasmResult setHttpCallResponseTrailers(ProxyMap trailers) {
         return next().setHttpCallResponseTrailers(trailers);
     }
 
     @Override
-    public WasmResult setGrpcReceiveInitialMetaData(Map<String, String> metadata) {
+    public WasmResult setGrpcReceiveInitialMetaData(ProxyMap metadata) {
         return next().setGrpcReceiveInitialMetaData(metadata);
     }
 
     @Override
-    public WasmResult setGrpcReceiveTrailerMetaData(Map<String, String> metadata) {
+    public WasmResult setGrpcReceiveTrailerMetaData(ProxyMap metadata) {
         return next().setGrpcReceiveTrailerMetaData(metadata);
     }
 
@@ -185,7 +182,7 @@ public WasmResult sendHttpResponse(
             int responseCode,
             byte[] responseCodeDetails,
             byte[] responseBody,
-            Map<String, String> additionalHeaders,
+            ProxyMap additionalHeaders,
             int grpcStatus) {
         return next().sendHttpResponse(
                         responseCode,
@@ -246,12 +243,7 @@ public WasmResult clearRouteCache() {
     }
 
     @Override
-    public int httpCall(
-            String uri,
-            HashMap<String, String> headers,
-            byte[] body,
-            HashMap<String, String> trailers,
-            int timeout)
+    public int httpCall(String uri, ProxyMap headers, byte[] body, ProxyMap trailers, int timeout)
             throws WasmException {
         return next().httpCall(uri, headers, body, trailers, timeout);
     }
@@ -259,9 +251,9 @@ public int httpCall(
     @Override
     public int dispatchHttpCall(
             String upstreamName,
-            HashMap<String, String> headers,
+            ProxyMap headers,
             byte[] body,
-            HashMap<String, String> trailers,
+            ProxyMap trailers,
             int timeoutMilliseconds)
             throws WasmException {
         return next().dispatchHttpCall(upstreamName, headers, body, trailers, timeoutMilliseconds);
diff --git a/src/main/java/io/roastedroot/proxywasm/Handler.java b/src/main/java/io/roastedroot/proxywasm/Handler.java
index 568024d..e4160d7 100644
--- a/src/main/java/io/roastedroot/proxywasm/Handler.java
+++ b/src/main/java/io/roastedroot/proxywasm/Handler.java
@@ -1,8 +1,5 @@
 package io.roastedroot.proxywasm;
 
-import java.util.HashMap;
-import java.util.Map;
-
 public interface Handler {
 
     default void log(LogLevel level, String message) throws WasmException {}
@@ -12,39 +9,39 @@ default LogLevel getLogLevel() throws WasmException {
     }
 
     // TODO: use a better type than Map so that we can support repeated headers
-    default Map<String, String> getHttpRequestHeaders() {
+    default ProxyMap getHttpRequestHeaders() {
         return null;
     }
 
-    default Map<String, String> getHttpRequestTrailers() {
+    default ProxyMap getHttpRequestTrailers() {
         return null;
     }
 
-    default Map<String, String> getHttpResponseHeaders() {
+    default ProxyMap getHttpResponseHeaders() {
         return null;
     }
 
-    default Map<String, String> getHttpResponseTrailers() {
+    default ProxyMap getHttpResponseTrailers() {
         return null;
     }
 
-    default Map<String, String> getHttpCallResponseHeaders() {
+    default ProxyMap getHttpCallResponseHeaders() {
         return null;
     }
 
-    default Map<String, String> getHttpCallResponseTrailers() {
+    default ProxyMap getHttpCallResponseTrailers() {
         return null;
     }
 
-    default Map<String, String> getGrpcReceiveInitialMetaData() {
+    default ProxyMap getGrpcReceiveInitialMetaData() {
         return null;
     }
 
-    default Map<String, String> getGrpcReceiveTrailerMetaData() {
+    default ProxyMap getGrpcReceiveTrailerMetaData() {
         return null;
     }
 
-    default Map<String, String> getCustomHeaders(int mapType) {
+    default ProxyMap getCustomHeaders(int mapType) {
         return null;
     }
 
@@ -198,7 +195,7 @@ default WasmResult sendHttpResponse(
             int responseCode,
             byte[] responseCodeDetails,
             byte[] responseBody,
-            Map<String, String> additionalHeaders,
+            ProxyMap additionalHeaders,
             int grpcStatus) {
         return WasmResult.UNIMPLEMENTED;
     }
@@ -291,7 +288,7 @@ default WasmResult setCustomBuffer(int bufferType, byte[] buffer) {
      * @param map     The header map to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setCustomHeaders(int mapType, Map<String, String> map) {
+    default WasmResult setCustomHeaders(int mapType, ProxyMap map) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -301,7 +298,7 @@ default WasmResult setCustomHeaders(int mapType, Map<String, String> map) {
      * @param headers The headers to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setHttpRequestHeaders(Map<String, String> headers) {
+    default WasmResult setHttpRequestHeaders(ProxyMap headers) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -311,7 +308,7 @@ default WasmResult setHttpRequestHeaders(Map<String, String> headers) {
      * @param trailers The trailers to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setHttpRequestTrailers(Map<String, String> trailers) {
+    default WasmResult setHttpRequestTrailers(ProxyMap trailers) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -321,7 +318,7 @@ default WasmResult setHttpRequestTrailers(Map<String, String> trailers) {
      * @param headers The headers to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setHttpResponseHeaders(Map<String, String> headers) {
+    default WasmResult setHttpResponseHeaders(ProxyMap headers) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -331,7 +328,7 @@ default WasmResult setHttpResponseHeaders(Map<String, String> headers) {
      * @param trailers The trailers to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setHttpResponseTrailers(Map<String, String> trailers) {
+    default WasmResult setHttpResponseTrailers(ProxyMap trailers) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -341,7 +338,7 @@ default WasmResult setHttpResponseTrailers(Map<String, String> trailers) {
      * @param headers The headers to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setHttpCallResponseHeaders(Map<String, String> headers) {
+    default WasmResult setHttpCallResponseHeaders(ProxyMap headers) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -351,7 +348,7 @@ default WasmResult setHttpCallResponseHeaders(Map<String, String> headers) {
      * @param trailers The trailers to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setHttpCallResponseTrailers(Map<String, String> trailers) {
+    default WasmResult setHttpCallResponseTrailers(ProxyMap trailers) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -361,7 +358,7 @@ default WasmResult setHttpCallResponseTrailers(Map<String, String> trailers) {
      * @param metadata The metadata to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setGrpcReceiveInitialMetaData(Map<String, String> metadata) {
+    default WasmResult setGrpcReceiveInitialMetaData(ProxyMap metadata) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -371,7 +368,7 @@ default WasmResult setGrpcReceiveInitialMetaData(Map<String, String> metadata) {
      * @param metadata The metadata to set
      * @return WasmResult indicating success or failure
      */
-    default WasmResult setGrpcReceiveTrailerMetaData(Map<String, String> metadata) {
+    default WasmResult setGrpcReceiveTrailerMetaData(ProxyMap metadata) {
         return WasmResult.UNIMPLEMENTED;
     }
 
@@ -384,20 +381,16 @@ default WasmResult clearRouteCache() {
     }
 
     default int httpCall(
-            String uri,
-            HashMap<String, String> headers,
-            byte[] body,
-            HashMap<String, String> trailers,
-            int timeoutMilliseconds)
+            String uri, ProxyMap headers, byte[] body, ProxyMap trailers, int timeoutMilliseconds)
             throws WasmException {
         throw new WasmException(WasmResult.UNIMPLEMENTED);
     }
 
     default int dispatchHttpCall(
             String upstreamName,
-            HashMap<String, String> headers,
+            ProxyMap headers,
             byte[] body,
-            HashMap<String, String> trailers,
+            ProxyMap trailers,
             int timeoutMilliseconds)
             throws WasmException {
         throw new WasmException(WasmResult.UNIMPLEMENTED);
diff --git a/src/main/java/io/roastedroot/proxywasm/Helpers.java b/src/main/java/io/roastedroot/proxywasm/Helpers.java
index 7182b46..e71f4ba 100644
--- a/src/main/java/io/roastedroot/proxywasm/Helpers.java
+++ b/src/main/java/io/roastedroot/proxywasm/Helpers.java
@@ -37,6 +37,13 @@ public static int len(byte[] value) {
         return value.length;
     }
 
+    public static int len(ProxyMap value) {
+        if (value == null) {
+            return 0;
+        }
+        return value.size();
+    }
+
     public static <T> int len(String value) {
         if (value == null) {
             return 0;
diff --git a/src/main/java/io/roastedroot/proxywasm/ProxyMap.java b/src/main/java/io/roastedroot/proxywasm/ProxyMap.java
new file mode 100644
index 0000000..34e97c5
--- /dev/null
+++ b/src/main/java/io/roastedroot/proxywasm/ProxyMap.java
@@ -0,0 +1,36 @@
+package io.roastedroot.proxywasm;
+
+import java.util.Map;
+
+public interface ProxyMap {
+
+    static ProxyMap of(String... values) {
+        if (values.length % 2 != 0) {
+            throw new IllegalArgumentException("values must be even");
+        }
+        ArrayProxyMap map = new ArrayProxyMap(values.length / 2);
+        for (int i = 0; i < values.length; i += 2) {
+            map.add(values[i], values[i + 1]);
+        }
+        return map;
+    }
+
+    static ProxyMap copyOf(Map<String, String> headers) {
+        if (headers == null) {
+            return null;
+        }
+        return new ArrayProxyMap(headers);
+    }
+
+    int size();
+
+    void add(String key, String value);
+
+    void put(String key, String value);
+
+    Iterable<? extends Map.Entry<String, String>> entries();
+
+    String get(String key);
+
+    void remove(String key);
+}
diff --git a/src/main/java/io/roastedroot/proxywasm/ProxyWasm.java b/src/main/java/io/roastedroot/proxywasm/ProxyWasm.java
index 3d71687..cac5208 100644
--- a/src/main/java/io/roastedroot/proxywasm/ProxyWasm.java
+++ b/src/main/java/io/roastedroot/proxywasm/ProxyWasm.java
@@ -34,8 +34,8 @@ public final class ProxyWasm implements Closeable {
     private Context activeContext;
 
     private HashMap<Integer, Context> contexts = new HashMap<>();
-    private Map<String, String> httpCallResponseHeaders;
-    private Map<String, String> httpCallResponseTrailers;
+    private ProxyMap httpCallResponseHeaders;
+    private ProxyMap httpCallResponseTrailers;
     private byte[] httpCallResponseBody;
     private HashMap<String, ForeignFunction> foreignFunctions = new HashMap<>();
 
@@ -120,12 +120,12 @@ public WasmResult done() {
             }
 
             @Override
-            public Map<String, String> getHttpCallResponseHeaders() {
+            public ProxyMap getHttpCallResponseHeaders() {
                 return httpCallResponseHeaders;
             }
 
             @Override
-            public Map<String, String> getHttpCallResponseTrailers() {
+            public ProxyMap getHttpCallResponseTrailers() {
                 return httpCallResponseTrailers;
             }
 
@@ -220,6 +220,12 @@ public static ProxyWasm.Builder builder() {
 
     public void sendHttpCallResponse(
             int calloutID, Map<String, String> headers, Map<String, String> trailers, byte[] body) {
+        this.sendHttpCallResponse(
+                calloutID, ProxyMap.copyOf(headers), ProxyMap.copyOf(trailers), body);
+    }
+
+    public void sendHttpCallResponse(
+            int calloutID, ProxyMap headers, ProxyMap trailers, byte[] body) {
 
         this.httpCallResponseHeaders = headers;
         this.httpCallResponseTrailers = trailers;
diff --git a/src/test/java/io/roastedroot/proxywasm/examples/HttpAuthRandomTest.java b/src/test/java/io/roastedroot/proxywasm/examples/HttpAuthRandomTest.java
index 821d780..d4253d4 100644
--- a/src/test/java/io/roastedroot/proxywasm/examples/HttpAuthRandomTest.java
+++ b/src/test/java/io/roastedroot/proxywasm/examples/HttpAuthRandomTest.java
@@ -8,10 +8,10 @@
 
 import com.dylibso.chicory.wasm.Parser;
 import io.roastedroot.proxywasm.Action;
+import io.roastedroot.proxywasm.ProxyMap;
 import io.roastedroot.proxywasm.ProxyWasm;
 import io.roastedroot.proxywasm.StartException;
 import java.nio.file.Path;
-import java.util.Map;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
@@ -45,7 +45,7 @@ public void onHttpRequestHeaders() throws StartException {
         try (var context = host.createHttpContext(handler)) {
 
             // Call OnRequestHeaders.
-            handler.setHttpRequestHeaders(Map.of("key", "value"));
+            handler.setHttpRequestHeaders(ProxyMap.of("key", "value"));
             var action = context.callOnRequestHeaders(false);
             Assertions.assertEquals(Action.PAUSE, action);
 
@@ -64,7 +64,7 @@ public void onHttpRequestHeaders() throws StartException {
     @Test
     public void onHttpCallResponse() throws StartException {
         var headers =
-                Map.of(
+                ProxyMap.of(
                         "HTTP/1.1", "200 OK",
                         "Date:", "Thu, 17 Sep 2020 02:47:07 GMT",
                         "Content-Type", "application/json",
@@ -78,7 +78,7 @@ public void onHttpCallResponse() throws StartException {
         try (var context = host.createHttpContext(handler)) {
 
             // Call OnRequestHeaders.
-            handler.setHttpRequestHeaders(Map.of());
+            handler.setHttpRequestHeaders(ProxyMap.of());
             var action = context.callOnRequestHeaders(false);
             assertEquals(Action.PAUSE, action);
 
@@ -101,7 +101,7 @@ public void onHttpCallResponse() throws StartException {
         try (var context = host.createHttpContext(handler)) {
 
             // Call OnRequestHeaders.
-            handler.setHttpRequestHeaders(Map.of());
+            handler.setHttpRequestHeaders(ProxyMap.of());
             var action = context.callOnRequestHeaders(false);
             assertEquals(Action.PAUSE, action);
 
@@ -116,7 +116,7 @@ public void onHttpCallResponse() throws StartException {
             assertNotNull(localResponse);
             assertEquals(403, localResponse.statusCode);
             assertEquals("access forbidden", string(localResponse.body));
-            assertEquals(Map.of("powered-by", "proxy-wasm-go-sdk!!"), localResponse.headers);
+            assertEquals(ProxyMap.of("powered-by", "proxy-wasm-go-sdk!!"), localResponse.headers);
 
             // CHeck Envoy logs.
             handler.assertLogsContain("access forbidden");
diff --git a/src/test/java/io/roastedroot/proxywasm/examples/HttpBodyTest.java b/src/test/java/io/roastedroot/proxywasm/examples/HttpBodyTest.java
index 817500c..f0f3036 100644
--- a/src/test/java/io/roastedroot/proxywasm/examples/HttpBodyTest.java
+++ b/src/test/java/io/roastedroot/proxywasm/examples/HttpBodyTest.java
@@ -8,11 +8,11 @@
 import com.dylibso.chicory.wasm.Parser;
 import io.roastedroot.proxywasm.Action;
 import io.roastedroot.proxywasm.HttpContext;
+import io.roastedroot.proxywasm.ProxyMap;
 import io.roastedroot.proxywasm.ProxyWasm;
 import io.roastedroot.proxywasm.StartException;
 import java.nio.charset.StandardCharsets;
 import java.nio.file.Path;
-import java.util.Map;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.BeforeEach;
@@ -47,7 +47,7 @@ public void testOnHttpRequestHeadersRemoveRequestHeader() throws StartException
 
         // Call OnRequestHeaders.
         handler.setHttpRequestHeaders(
-                Map.of(
+                ProxyMap.of(
                         "content-length", "10",
                         "buffer-operation", "replace"));
         var action = httpContext.callOnRequestHeaders(false);
@@ -56,7 +56,7 @@ public void testOnHttpRequestHeadersRemoveRequestHeader() throws StartException
         Assertions.assertEquals(Action.CONTINUE, action);
 
         var headers = handler.getHttpRequestHeaders();
-        assertEquals(Map.of("buffer-operation", "replace"), headers);
+        assertEquals(ProxyMap.of("buffer-operation", "replace"), headers);
     }
 
     @Test
@@ -88,7 +88,7 @@ public void testOnHttpRequestBodyPauseUntilEOS() throws StartException {
     public void testOnHttpRequestBodyAppend() throws StartException {
         // Call callOnRequestBody
         handler.setHttpRequestHeaders(
-                Map.of(
+                ProxyMap.of(
                         "content-length", "10",
                         "buffer-operation", "append"));
 
@@ -111,7 +111,7 @@ public void testOnHttpRequestBodyAppend() throws StartException {
     public void testOnHttpRequestBodyPrepend() throws StartException {
         // Call callOnRequestBody
         handler.setHttpRequestHeaders(
-                Map.of(
+                ProxyMap.of(
                         "content-length", "10",
                         "buffer-operation", "prepend"));
 
@@ -134,7 +134,7 @@ public void testOnHttpRequestBodyPrepend() throws StartException {
     public void testOnHttpRequestBodyReplace() throws StartException {
         // Call callOnRequestBody
         handler.setHttpRequestHeaders(
-                Map.of(
+                ProxyMap.of(
                         "content-length", "10",
                         "buffer-operation", "replace"));
 
@@ -157,7 +157,7 @@ public void testOnHttpResponseBodyAppend() throws StartException {
 
         // Call OnRequestHeaders
         handler.setHttpRequestHeaders(
-                Map.of(
+                ProxyMap.of(
                         "buffer-replace-at", "response",
                         "content-length", "10",
                         "buffer-operation", "append"));
@@ -178,7 +178,7 @@ public void testOnHttpResponseBodyPrepend() throws StartException {
 
         // Call OnRequestHeaders
         handler.setHttpRequestHeaders(
-                Map.of(
+                ProxyMap.of(
                         "buffer-replace-at", "response",
                         "content-length", "10",
                         "buffer-operation", "prepend"));
@@ -199,7 +199,7 @@ public void testOnHttpResponseBodyReplace() throws StartException {
 
         // Call OnRequestHeaders
         handler.setHttpRequestHeaders(
-                Map.of(
+                ProxyMap.of(
                         "buffer-replace-at", "response",
                         "content-length", "10",
                         "buffer-operation", "replace"));
diff --git a/src/test/java/io/roastedroot/proxywasm/examples/HttpHeadersTest.java b/src/test/java/io/roastedroot/proxywasm/examples/HttpHeadersTest.java
index f423b97..c9e4fcc 100644
--- a/src/test/java/io/roastedroot/proxywasm/examples/HttpHeadersTest.java
+++ b/src/test/java/io/roastedroot/proxywasm/examples/HttpHeadersTest.java
@@ -5,10 +5,10 @@
 
 import com.dylibso.chicory.wasm.Parser;
 import io.roastedroot.proxywasm.Action;
+import io.roastedroot.proxywasm.ProxyMap;
 import io.roastedroot.proxywasm.ProxyWasm;
 import io.roastedroot.proxywasm.StartException;
 import java.nio.file.Path;
-import java.util.Map;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
@@ -28,7 +28,7 @@ public void onHttpRequestHeaders() throws StartException {
             try (var host = proxyWasm.createHttpContext(handler)) {
                 id = host.id();
                 handler.setHttpRequestHeaders(
-                        Map.of(
+                        ProxyMap.of(
                                 "key1", "value1",
                                 "key2", "value2"));
                 var action = host.callOnRequestHeaders(false);
@@ -60,7 +60,7 @@ public void onHttpResponseHeaders() throws StartException {
             try (var host = proxyWasm.createHttpContext(handler)) {
                 id = host.id();
                 handler.setHttpResponseHeaders(
-                        Map.of(
+                        ProxyMap.of(
                                 "key1", "value1",
                                 "key2", "value2"));
                 var action = host.callOnResponseHeaders(false);
@@ -69,11 +69,11 @@ public void onHttpResponseHeaders() throws StartException {
 
             // Check headers
             assertEquals(
-                    Map.of(
+                    ProxyMap.of(
                             "key1", "value1",
                             "key2", "value2",
-                            "x-wasm-header", "x-value",
-                            "x-proxy-wasm-go-sdk-example", "http_headers"),
+                            "x-proxy-wasm-go-sdk-example", "http_headers",
+                            "x-wasm-header", "x-value"),
                     handler.getHttpResponseHeaders());
 
             // Check logs
diff --git a/src/test/java/io/roastedroot/proxywasm/examples/HttpRoutingTest.java b/src/test/java/io/roastedroot/proxywasm/examples/HttpRoutingTest.java
index 4015662..9e87c19 100644
--- a/src/test/java/io/roastedroot/proxywasm/examples/HttpRoutingTest.java
+++ b/src/test/java/io/roastedroot/proxywasm/examples/HttpRoutingTest.java
@@ -35,7 +35,7 @@ public void canary() throws StartException {
                 assertEquals(Action.CONTINUE, action);
 
                 // Get and verify modified headers
-                Map<String, String> resultHeaders = handler.getHttpRequestHeaders();
+                var resultHeaders = handler.getHttpRequestHeaders();
                 assertEquals(1, resultHeaders.size());
                 assertEquals("my-host.com-canary", resultHeaders.get(":authority"));
             }
@@ -62,7 +62,7 @@ public void nonCanary() throws StartException {
                 assertEquals(Action.CONTINUE, action);
 
                 // Get and verify modified headers
-                Map<String, String> resultHeaders = handler.getHttpRequestHeaders();
+                var resultHeaders = handler.getHttpRequestHeaders();
                 assertEquals(1, resultHeaders.size());
                 assertEquals("my-host.com", resultHeaders.get(":authority"));
             }
diff --git a/src/test/java/io/roastedroot/proxywasm/examples/MockHandler.java b/src/test/java/io/roastedroot/proxywasm/examples/MockHandler.java
index cafb021..9205968 100644
--- a/src/test/java/io/roastedroot/proxywasm/examples/MockHandler.java
+++ b/src/test/java/io/roastedroot/proxywasm/examples/MockHandler.java
@@ -5,11 +5,13 @@
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import io.roastedroot.proxywasm.Action;
+import io.roastedroot.proxywasm.ArrayProxyMap;
 import io.roastedroot.proxywasm.ChainedHandler;
 import io.roastedroot.proxywasm.Handler;
 import io.roastedroot.proxywasm.Helpers;
 import io.roastedroot.proxywasm.LogLevel;
 import io.roastedroot.proxywasm.MetricType;
+import io.roastedroot.proxywasm.ProxyMap;
 import io.roastedroot.proxywasm.StreamType;
 import io.roastedroot.proxywasm.WasmException;
 import io.roastedroot.proxywasm.WasmResult;
@@ -30,14 +32,14 @@ public static class HttpResponse {
         public final int statusCode;
         public final byte[] statusCodeDetails;
         public final byte[] body;
-        public final Map<String, String> headers;
+        public final ProxyMap headers;
         public final int grpcStatus;
 
         public HttpResponse(
                 int responseCode,
                 byte[] responseCodeDetails,
                 byte[] responseBody,
-                Map<String, String> additionalHeaders,
+                ProxyMap additionalHeaders,
                 int grpcStatus) {
             this.statusCode = responseCode;
             this.statusCodeDetails = responseCodeDetails;
@@ -50,12 +52,12 @@ public HttpResponse(
     final ArrayList<String> loggedMessages = new ArrayList<>();
 
     private int tickPeriodMilliseconds;
-    private Map<String, String> httpRequestHeaders = new HashMap<>();
-    private Map<String, String> httpRequestTrailers = new HashMap<>();
-    private Map<String, String> httpResponseHeaders = new HashMap<>();
-    private Map<String, String> httpResponseTrailers = new HashMap<>();
-    private Map<String, String> grpcReceiveInitialMetadata = new HashMap<>();
-    private Map<String, String> grpcReceiveTrailerMetadata = new HashMap<>();
+    private ProxyMap httpRequestHeaders = new ArrayProxyMap();
+    private ProxyMap httpRequestTrailers = new ArrayProxyMap();
+    private ProxyMap httpResponseHeaders = new ArrayProxyMap();
+    private ProxyMap httpResponseTrailers = new ArrayProxyMap();
+    private ProxyMap grpcReceiveInitialMetadata = new ArrayProxyMap();
+    private ProxyMap grpcReceiveTrailerMetadata = new ArrayProxyMap();
     private HttpResponse senthttpResponse;
 
     private byte[] funcCallData = new byte[0];
@@ -127,67 +129,79 @@ public int getTickPeriodMilliseconds() {
     }
 
     @Override
-    public Map<String, String> getHttpRequestHeaders() {
+    public ProxyMap getHttpRequestHeaders() {
         return httpRequestHeaders;
     }
 
     @Override
-    public Map<String, String> getHttpRequestTrailers() {
+    public ProxyMap getHttpRequestTrailers() {
         return httpRequestTrailers;
     }
 
     @Override
-    public Map<String, String> getHttpResponseHeaders() {
+    public ProxyMap getHttpResponseHeaders() {
         return httpResponseHeaders;
     }
 
     @Override
-    public Map<String, String> getHttpResponseTrailers() {
+    public ProxyMap getHttpResponseTrailers() {
         return httpResponseTrailers;
     }
 
     @Override
-    public Map<String, String> getGrpcReceiveInitialMetaData() {
+    public ProxyMap getGrpcReceiveInitialMetaData() {
         return grpcReceiveInitialMetadata;
     }
 
     @Override
-    public Map<String, String> getGrpcReceiveTrailerMetaData() {
+    public ProxyMap getGrpcReceiveTrailerMetaData() {
         return grpcReceiveTrailerMetadata;
     }
 
     @Override
-    public WasmResult setHttpRequestHeaders(Map<String, String> headers) {
+    public WasmResult setHttpRequestHeaders(ProxyMap headers) {
         this.httpRequestHeaders = headers;
         return WasmResult.OK;
     }
 
+    public WasmResult setHttpRequestHeaders(Map<String, String> headers) {
+        return this.setHttpRequestHeaders(new ArrayProxyMap(headers));
+    }
+
     @Override
-    public WasmResult setHttpRequestTrailers(Map<String, String> trailers) {
+    public WasmResult setHttpRequestTrailers(ProxyMap trailers) {
         this.httpRequestTrailers = trailers;
         return WasmResult.OK;
     }
 
+    public WasmResult setHttpRequestTrailers(Map<String, String> headers) {
+        return this.setHttpRequestTrailers(new ArrayProxyMap(headers));
+    }
+
     @Override
-    public WasmResult setHttpResponseHeaders(Map<String, String> headers) {
+    public WasmResult setHttpResponseHeaders(ProxyMap headers) {
         this.httpResponseHeaders = headers;
         return WasmResult.OK;
     }
 
+    public WasmResult setHttpResponseHeaders(Map<String, String> headers) {
+        return this.setHttpResponseHeaders(new ArrayProxyMap(headers));
+    }
+
     @Override
-    public WasmResult setHttpResponseTrailers(Map<String, String> trailers) {
+    public WasmResult setHttpResponseTrailers(ProxyMap trailers) {
         this.httpResponseTrailers = trailers;
         return WasmResult.OK;
     }
 
     @Override
-    public WasmResult setGrpcReceiveInitialMetaData(Map<String, String> metadata) {
+    public WasmResult setGrpcReceiveInitialMetaData(ProxyMap metadata) {
         this.grpcReceiveInitialMetadata = metadata;
         return WasmResult.OK;
     }
 
     @Override
-    public WasmResult setGrpcReceiveTrailerMetaData(Map<String, String> metadata) {
+    public WasmResult setGrpcReceiveTrailerMetaData(ProxyMap metadata) {
         this.grpcReceiveTrailerMetadata = metadata;
         return WasmResult.OK;
     }
@@ -271,7 +285,7 @@ public WasmResult sendHttpResponse(
             int responseCode,
             byte[] responseCodeDetails,
             byte[] responseBody,
-            Map<String, String> additionalHeaders,
+            ProxyMap additionalHeaders,
             int grpcStatus) {
         this.senthttpResponse =
                 new HttpResponse(
@@ -298,16 +312,16 @@ public enum Type {
         public final String uri;
         public final Object headers;
         public final byte[] body;
-        public final HashMap<String, String> trailers;
+        public final ProxyMap trailers;
         public final int timeoutMilliseconds;
 
         public HttpCall(
                 int id,
                 Type callType,
                 String uri,
-                HashMap<String, String> headers,
+                ProxyMap headers,
                 byte[] body,
-                HashMap<String, String> trailers,
+                ProxyMap trailers,
                 int timeoutMilliseconds) {
             this.id = id;
             this.callType = callType;
@@ -320,7 +334,7 @@ public HttpCall(
     }
 
     private final AtomicInteger lastCallId = new AtomicInteger(0);
-    private final HashMap<Integer, HttpCall> httpCalls = new HashMap<>();
+    private final HashMap<Integer, HttpCall> httpCalls = new HashMap();
 
     public HashMap<Integer, HttpCall> getHttpCalls() {
         return httpCalls;
@@ -328,11 +342,7 @@ public HashMap<Integer, HttpCall> getHttpCalls() {
 
     @Override
     public int httpCall(
-            String uri,
-            HashMap<String, String> headers,
-            byte[] body,
-            HashMap<String, String> trailers,
-            int timeoutMilliseconds)
+            String uri, ProxyMap headers, byte[] body, ProxyMap trailers, int timeoutMilliseconds)
             throws WasmException {
         var id = lastCallId.incrementAndGet();
         HttpCall value =
@@ -351,9 +361,9 @@ public int httpCall(
     @Override
     public int dispatchHttpCall(
             String upstreamName,
-            HashMap<String, String> headers,
+            ProxyMap headers,
             byte[] body,
-            HashMap<String, String> trailers,
+            ProxyMap trailers,
             int timeoutMilliseconds)
             throws WasmException {
         var id = lastCallId.incrementAndGet();
@@ -385,8 +395,8 @@ public Metric(int id, MetricType type, String name) {
     }
 
     private final AtomicInteger lastMetricId = new AtomicInteger(0);
-    private HashMap<Integer, Metric> metrics = new HashMap<>();
-    private HashMap<String, Metric> metricsByName = new HashMap<>();
+    private HashMap<Integer, Metric> metrics = new HashMap();
+    private HashMap<String, Metric> metricsByName = new HashMap();
 
     @Override
     public int defineMetric(MetricType type, String name) throws WasmException {