@ws-kit/memory

In-memory adapters for WS-Kit. Provides a zero-dependency pub/sub registry and token-bucket rate limiter for single-instance development and tests (Bun/Node.js).

When to use

• Local development, unit tests, or single-server deployments
• Exact subscriber counts without external brokers
• Deterministic rate-limit testing via injectable clocks
• ⚠️ Not distributed — no cross-process/state persistence

What you get

• memoryPubSub() — In-memory topic index (Map<topic, Set<clientId>>). Implements publish, subscribe, unsubscribe, getSubscribers, listTopics, hasTopic, and replace for bulk topic swaps. excludeSelf is unsupported (no sender context).
• memoryRateLimiter(policy, opts?) — Token-bucket limiter with per-key mutex to prevent double spending. Supports prefix isolation, getPolicy(), dispose(), and optional clock injection for deterministic tests.
• Types: MemoryPubSubAdapter, MemoryRateLimiterOptions, Clock.

Installation

bun add @ws-kit/memory

Quick start: pub/sub (development)

import { createRouter, withZod, message } from "@ws-kit/zod";
import { withPubSub } from "@ws-kit/plugins";
import { memoryPubSub } from "@ws-kit/memory";
import { z } from "zod";

const Notify = message("NOTIFY", { text: z.string() });

const router = createRouter()
  .plugin(withZod())
  .plugin(withPubSub({ adapter: memoryPubSub() })); // exact local fan-out

router.on(Notify, async (ctx) => {
  await ctx.topics.subscribe("room:lobby");
  await ctx.publish("room:lobby", Notify, { text: "Hi!" });
});

Quick start: rate limiting

import { createRouter } from "@ws-kit/core";
import { rateLimit, keyPerUserPerType } from "@ws-kit/rate-limit";
import { memoryRateLimiter } from "@ws-kit/memory";

const limiter = memoryRateLimiter({
  capacity: 100, // bucket size
  tokensPerSecond: 10, // refill rate
  prefix: "api:", // optional isolation when sharing a backend
});

const router = createRouter().use(
  rateLimit({
    limiter,
    key: keyPerUserPerType,
    cost: () => 1,
  }),
);

Notes

• Pub/sub is process-local only; restart clears subscriptions.
• Rate limiter is process-local; use @ws-kit/redis or a Durable Objects adapter for shared limits.
• For deterministic tests, pass { clock: { now: () => number } } to memoryRateLimiter().