feat: Redis caching layer with tests

Makefile

@@ -0,0 +1,2 @@
+cache-test:
+	docker compose run --rm app-test

docker-compose.yml

@@ -21,6 +21,20 @@ services:
     volumes:
       - redisdata:/data
 
+  app-test:
+    build:
+      context: .
+      target: deps
+    volumes:
+      - .:/app
+      - /app/node_modules
+    env_file:
+      - .env
+    depends_on:
+      - postgres
+      - redis
+    command: sh -c "npx drizzle-kit push && npx vitest run src/test/cache.test.ts"
+
 volumes:
   pgdata:
   redisdata:

src/cache/index.ts

@@ -0,0 +1,97 @@
+import { redis } from "../config/redis.js";
+import { logger } from "../utils/logger.js";
+import { Counter } from "prom-client";
+
+const DEFAULT_TTL = 60;
+
+export const cacheHits = new Counter({
+  name: "cache_hits_total",
+  help: "Total cache hits",
+  labelNames: ["namespace"],
+});
+
+export const cacheMisses = new Counter({
+  name: "cache_misses_total",
+  help: "Total cache misses",
+  labelNames: ["namespace"],
+});
+
+export interface CacheOptions {
+  ttl?: number;
+  prefix?: string;
+}
+
+export function cacheKey(
+  namespace: string,
+  ...parts: (string | number)[]
+): string {
+  return `chainlearn:${namespace}:${parts.join(":")}`;
+}
+
+export async function cacheGet<T>(
+  namespace: string,
+  key: string,
+): Promise<T | null> {
+  try {
+    const raw = await redis.get(key);
+    if (!raw) {
+      cacheMisses.labels({ namespace }).inc();
+      return null;
+    }
+    cacheHits.labels({ namespace }).inc();
+    return JSON.parse(raw) as T;
+  } catch (err) {
+    logger.warn(
+      { err, key },
+      "Cache read failed - Degrading gracefully to database",
+    );
+    return null;
+  }
+}
+
+export async function cacheSet<T>(
+  key: string,
+  value: T,
+  ttl: number = DEFAULT_TTL,
+): Promise<void> {
+  try {
+    await redis.setex(key, ttl, JSON.stringify(value));
+  } catch (err) {
+    logger.warn({ err, key }, "Cache write failed");
+  }
+}
+
+/**
+ * Deletes precise keys safely. Avoids high-latency KEYS scanning in production.
+ */
+export async function cacheDel(key: string): Promise<void> {
+  try {
+    await redis.del(key);
+  } catch (err) {
+    logger.warn({ err, key }, "Cache delete failed");
+  }
+}
+
+/**
+ * Safely clears groups of keys using SCAN instead of KEYS *
+ */
+export async function cacheInvalidatePattern(pattern: string): Promise<void> {
+  try {
+    let cursor = "0";
+    do {
+      const [newCursor, keys] = await redis.scan(
+        cursor,
+        "MATCH",
+        pattern,
+        "COUNT",
+        100,
+      );
+      cursor = newCursor;
+      if (keys.length > 0) {
+        await redis.del(...keys);
+      }
+    } while (cursor !== "0");
+  } catch (err) {
+    logger.warn({ err, pattern }, "Pattern cache invalidation failed");
+  }
+}

src/cache/warmer.ts

@@ -0,0 +1,20 @@
+import { cacheSet, cacheKey } from "./index.js";
+import { logger } from "../utils/logger.js";
+import { courseService } from "../modules/courses/course.service.js";
+
+export async function warmCourseCache(): Promise<void> {
+  try {
+    logger.info("Starting course listing cache warming cycle...");
+
+    const landingPageQuery = { page: 1, limit: 20 };
+    const data = await courseService.listCourses(null, landingPageQuery);
+
+    const key = cacheKey("courses", "list", "all", 1, 20);
+
+    await cacheSet(key, data, 60);
+
+    logger.info("Course listing cache successfully warmed");
+  } catch (err) {
+    logger.error({ err }, "Cache warming cycle failed step execution");
+  }
+}