diff --git a/src/main/java/hse/java/lectures/lecture6/tasks/queue/BoundedBlockingQueue.java b/src/main/java/hse/java/lectures/lecture6/tasks/queue/BoundedBlockingQueue.java
index 816f3ee6..c5794f3d 100644
--- a/src/main/java/hse/java/lectures/lecture6/tasks/queue/BoundedBlockingQueue.java
+++ b/src/main/java/hse/java/lectures/lecture6/tasks/queue/BoundedBlockingQueue.java
@@ -1,25 +1,48 @@
 package hse.java.lectures.lecture6.tasks.queue;
 
-public class BoundedBlockingQueue<T> {
+import java.util.ArrayDeque;
+import java.util.Queue;
 
+public class BoundedBlockingQueue<T> {
+    private final Queue<T> queue = new ArrayDeque<>();
+    private final int capacity;
 
     public BoundedBlockingQueue(int capacity) {
-
+        if(capacity <= 0){
+            throw new IllegalArgumentException("Capacity <= 0 :^(");
+        }
+        this.capacity = capacity;
     }
 
-    public void put(T item) throws InterruptedException {
+    public synchronized void put(T item) throws InterruptedException{
+        if(item == null){
+            throw new NullPointerException("not null pls");
+        }
 
+        while(queue.size() == capacity()){
+            wait();
+        }
+
+        queue.add(item);
+        notifyAll();
     }
 
-    public T take() throws InterruptedException {
-        return null;
+    public synchronized T take() throws InterruptedException{
+        while(queue.isEmpty()){
+            wait();
+        }
+
+        T item = queue.remove();
+        notifyAll();
+
+        return item;
     }
 
-    public int size() {
-        return 0;
+    public synchronized int size() {
+        return queue.size();
     }
 
     public int capacity() {
-        return 0;
+        return capacity;
     }
-}
+}
\ No newline at end of file
diff --git a/src/main/java/hse/java/lectures/lesson7/dau/DauServiceImplementation.java b/src/main/java/hse/java/lectures/lesson7/dau/DauServiceImplementation.java
new file mode 100644
index 00000000..198f6668
--- /dev/null
+++ b/src/main/java/hse/java/lectures/lesson7/dau/DauServiceImplementation.java
@@ -0,0 +1,61 @@
+package hse.java.lectures.lesson7.dau;
+
+import java.time.Clock;
+import java.time.LocalDate;
+import java.util.*;
+import java.util.concurrent.ConcurrentHashMap;
+
+public class DauServiceImplementation implements DauService {
+    private final Clock clock;
+    private volatile LocalDate current;
+
+    private final ConcurrentHashMap<Integer, Set<Integer>> today = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<Integer, Set<Integer>> yesterday = new ConcurrentHashMap<>();
+
+    public DauServiceImplementation(Clock clock) {
+        this.clock = clock;
+        this.current = LocalDate.now(clock);
+    }
+
+    private void isNextDay() {
+        LocalDate now = LocalDate.now(clock);
+
+        if (!now.equals(current)) {
+            synchronized (this) {
+                if (!now.equals(current)) {
+                    yesterday.clear();
+                    yesterday.putAll(today);
+
+                    today.clear();
+
+                    current = now;
+                }
+            }
+        }
+    }
+
+    @Override
+    public void postEvent(Event event) {
+        isNextDay();
+        today.computeIfAbsent(event.authorId(), a -> ConcurrentHashMap.newKeySet()).add(event.userId());
+    }
+
+    @Override
+    public Map<Integer, Long> getDauStatistics(List<Integer> authorIds) {
+        isNextDay();
+
+        Map<Integer, Long> result = new HashMap<>();
+
+        for (Integer authorId : authorIds) {
+            Set<Integer> users = yesterday.get(authorId);
+            result.put(authorId, users == null ? 0L : (long) users.size());
+        }
+
+        return result;
+    }
+
+    @Override
+    public Long getAuthorDauStatistics(int authorId) {
+        return getDauStatistics(List.of(authorId)).get(authorId);
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/hse/java/lectures/lecture7/DauServiceTest.java b/src/test/java/hse/java/lectures/lecture7/DauServiceTest.java
new file mode 100644
index 00000000..92a46e48
--- /dev/null
+++ b/src/test/java/hse/java/lectures/lecture7/DauServiceTest.java
@@ -0,0 +1,116 @@
+package hse.java.lectures.lecture7;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Tag;
+import org.junit.jupiter.api.Test;
+
+import java.time.*;
+import java.util.List;
+import java.util.Map;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import hse.java.lectures.lesson7.dau.*;
+
+@Tag("Dau")
+class DauServiceTest {
+
+    private MutableClock clock;
+    private DauServiceImplementation service;
+
+    private static final ZoneId ZONE = ZoneOffset.UTC;
+
+    @BeforeEach
+    void setUp() {
+        clock = new MutableClock(LocalDate.of(2026, 3, 21).atStartOfDay(ZONE).toInstant(), ZONE);
+
+        service = new DauServiceImplementation(clock);
+    }
+
+    private void setDate(LocalDate date) {
+        clock.setInstant(date.atStartOfDay(ZONE).toInstant());
+    }
+
+    @Test
+    void singleUser_singleClick() {
+        setDate(LocalDate.of(2026, 3, 20));
+        service.postEvent(new Event(1, 100));
+
+        setDate(LocalDate.of(2026, 3, 21));
+
+        Long result = service.getAuthorDauStatistics(100);
+
+        assertEquals(1L, result);
+    }
+
+    @Test
+    void sameUser_multipleClicks() {
+        setDate(LocalDate.of(2026, 3, 20));
+
+        service.postEvent(new Event(1, 100));
+        service.postEvent(new Event(1, 100));
+        service.postEvent(new Event(1, 100));
+
+        setDate(LocalDate.of(2026, 3, 21));
+
+        assertEquals(1L, service.getAuthorDauStatistics(100));
+    }
+
+    @Test
+    void multipleUsers() {
+        setDate(LocalDate.of(2026, 3, 20));
+
+        service.postEvent(new Event(1, 100));
+        service.postEvent(new Event(2, 100));
+        service.postEvent(new Event(3, 100));
+
+        setDate(LocalDate.of(2026, 3, 21));
+
+        assertEquals(3L, service.getAuthorDauStatistics(100));
+    }
+
+    @Test
+    void differentAuthors() {
+        setDate(LocalDate.of(2026, 3, 20));
+
+        service.postEvent(new Event(1, 100));
+        service.postEvent(new Event(2, 200));
+
+        setDate(LocalDate.of(2026, 3, 21));
+
+        Map<Integer, Long> stats = service.getDauStatistics(List.of(100, 200));
+
+        assertEquals(1L, stats.get(100));
+        assertEquals(1L, stats.get(200));
+    }
+
+    @Test
+    void emptyClick() {
+        Map<Integer, Long> stats = service.getDauStatistics(List.of(100));
+
+        assertEquals(0L, stats.get(100));
+    }
+
+    @Test
+    void isTodayClicks() {
+        service.postEvent(new Event(1, 100));
+
+        assertEquals(0L, service.getAuthorDauStatistics(100));
+    }
+
+    @Test
+    void isDataClear() {
+        setDate(LocalDate.of(2026, 3, 20));
+        service.postEvent(new Event(1, 100));
+
+        setDate(LocalDate.of(2026, 3, 21));
+        service.postEvent(new Event(2, 100));
+
+        assertEquals(1L, service.getAuthorDauStatistics(100));
+
+        setDate(LocalDate.of(2026, 3, 22));
+        service.postEvent(new Event(3, 100));
+
+        assertEquals(1L, service.getAuthorDauStatistics(100));
+    }
+}
diff --git a/src/test/java/hse/java/lectures/lecture7/MutableClock.java b/src/test/java/hse/java/lectures/lecture7/MutableClock.java
new file mode 100644
index 00000000..a2c0d043
--- /dev/null
+++ b/src/test/java/hse/java/lectures/lecture7/MutableClock.java
@@ -0,0 +1,34 @@
+package hse.java.lectures.lecture7;
+
+import lombok.Setter;
+
+import java.time.Clock;
+import java.time.Instant;
+import java.time.ZoneId;
+
+class MutableClock extends Clock {
+
+    @Setter
+    private Instant instant;
+    private final ZoneId zone;
+
+    public MutableClock(Instant instant, ZoneId zone) {
+        this.instant = instant;
+        this.zone = zone;
+    }
+
+    @Override
+    public ZoneId getZone() {
+        return zone;
+    }
+
+    @Override
+    public Clock withZone(ZoneId zone) {
+        return new MutableClock(instant, zone);
+    }
+
+    @Override
+    public Instant instant() {
+        return instant;
+    }
+}
\ No newline at end of file