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lru-cache TTL eviction and size limits: working versions (tested 2026-10-15)

Cache computed values with lru-cache, covering max entries, TTL expiry via fake timers, and getOrSet style populate helpers offline.

passed3 passed · 0 failed2026-10-15 16:01 UTC
Status
passed
Last passed
2026-10-15 16:01 UTC
Tests
3 / 3
Language
TypeScript
Runtime
node v22.23.3
pinned versions3
lru-cache@11.5.3@types/node@26.6.5tsx@4.23.15
run it
npm install --no-audit --no-fund --ignore-scripts=false
npm test
test environment
node v22.23.3
linux 6.17.0-1022-azure
x64
runner: github-actions 38764699834

The code

Exactly the files that passed. Your agent can pull them with get_recipe("lru-cache-ttl") (install), or see them on GitHub.

package.json
{
  "name": "lru-cache-ttl",
  "private": true,
  "type": "module",
  "scripts": {
    "test": "node --import tsx --test test/*.test.ts"
  },
  "dependencies": {"lru-cache":"11.5.3"},
  "devDependencies": {"@types/node":"26.6.5","tsx":"4.23.15"}
}
src/cache.ts
import { LRUCache } from "lru-cache";

export type User = { id: string; name: string };

export function createUserCache(max = 100, ttlMs = 60_000) {
  const cache = new LRUCache<string, User>({
    max,
    ttl: ttlMs,
    // Use Date so node:test fake timers control expiry
    perf: { now: () => Date.now() },
  });

  return {
    get(id: string) {
      return cache.get(id);
    },
    set(user: User) {
      cache.set(user.id, user);
      return user;
    },
    async getOrFetch(id: string, fetch: (id: string) => Promise<User>) {
      const hit = cache.get(id);
      if (hit) return hit;
      const user = await fetch(id);
      cache.set(id, user);
      return user;
    },
    size() {
      return cache.size;
    },
    clear() {
      cache.clear();
    },
  };
}
test/cache.test.ts
import { test, mock } from "node:test";
import assert from "node:assert/strict";
import { createUserCache } from "../src/cache.ts";

test("evicts least recently used when full", () => {
  const cache = createUserCache(2, 60_000);
  cache.set({ id: "a", name: "Ada" });
  cache.set({ id: "b", name: "Bob" });
  cache.get("a");
  cache.set({ id: "c", name: "Cid" });
  assert.equal(cache.get("b"), undefined);
  assert.equal(cache.get("a")?.name, "Ada");
  assert.equal(cache.size(), 2);
});

test("expires entries after TTL with fake timers", async () => {
  mock.timers.enable({ apis: ["Date", "setTimeout"], now: 1_000 });
  const cache = createUserCache(10, 5_000);
  cache.set({ id: "a", name: "Ada" });
  assert.equal(cache.get("a")?.name, "Ada");
  mock.timers.tick(6_000);
  assert.equal(cache.get("a"), undefined);
  mock.timers.reset();
});

test("getOrFetch populates once", async () => {
  const cache = createUserCache();
  let calls = 0;
  const fetch = async (id: string) => {
    calls++;
    return { id, name: "Ada" };
  };
  assert.equal((await cache.getOrFetch("a", fetch)).name, "Ada");
  assert.equal((await cache.getOrFetch("a", fetch)).name, "Ada");
  assert.equal(calls, 1);
});

Connect to ProvenPin

Add the free MCP server so your agent can pull this recipe and others like it. Same setup as the docs.

terminal
claude mcp add --transport http provenpin https://mcp.provenpin.com/mcp

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