Rate Limiter

createRateLimiter

Signature

function createRateLimiter(config: RateLimiterConfig): {
  attempt(key: string): Promise<RateLimitResult>;
  reset(key: string): Promise<void>;
}

Creates a rate limiter with a sliding window strategy. Returns an object with attempt and reset methods.

import { createRateLimiter } from 'ideal-auth';

const loginLimiter = createRateLimiter({
  maxAttempts: 5,
  windowMs: 15 * 60 * 1000, // 15 minutes
});

---

RateLimiterConfig

interface RateLimiterConfig {
  maxAttempts: number;
  windowMs: number;
  store?: RateLimitStore;
}

Field	Type	Required	Default
maxAttempts	number	Yes	—
windowMs	number (milliseconds)	Yes	—
store	RateLimitStore	No	MemoryRateLimitStore

• maxAttempts — Maximum number of attempts allowed within the window before rate limiting takes effect.
• windowMs — Duration of the sliding window in milliseconds. The attempt count resets after this period.
• store — A backing store for tracking attempt counts. Defaults to an in-memory store. Provide a custom implementation for multi-process or distributed deployments.

---

attempt

attempt(key: string): Promise<RateLimitResult>

Records an attempt for the given key and returns the rate limit status.

const result = await loginLimiter.attempt('user@example.com');

if (!result.allowed) {
  return {
    error: `Too many attempts. Try again after ${result.resetAt.toISOString()}.`,
  };
}

// Proceed with login logic

RateLimitResult

interface RateLimitResult {
  allowed: boolean;
  remaining: number;
  resetAt: Date;
}

Field	Type	Description
allowed	boolean	true if the attempt is within the limit, false if rate limited
remaining	number	Number of attempts remaining in the current window (never goes negative)
resetAt	Date	When the current window expires and the count resets

const limiter = createRateLimiter({
  maxAttempts: 3,
  windowMs: 60_000,
});

await limiter.attempt('key'); // { allowed: true,  remaining: 2, resetAt: ... }
await limiter.attempt('key'); // { allowed: true,  remaining: 1, resetAt: ... }
await limiter.attempt('key'); // { allowed: true,  remaining: 0, resetAt: ... }
await limiter.attempt('key'); // { allowed: false, remaining: 0, resetAt: ... }

---

reset

reset(key: string): Promise<void>

Clears the rate limit for the given key, resetting its attempt count to zero. Useful after a successful action (e.g., clearing the login limiter after a successful login).

const success = await auth().attempt({ email, password });

if (success) {
  // Clear rate limit on successful login
  await loginLimiter.reset(email);
  redirect('/dashboard');
}

---

MemoryRateLimitStore

import { MemoryRateLimitStore } from 'ideal-auth';

The default in-memory store used by createRateLimiter when no store option is provided. Suitable for single-process deployments.

Behavior

Property	Value
Maximum entries	10,000
Cleanup interval	Every 60 seconds
Eviction	Expired entries are removed first
Full store	New keys are rejected when the store is full of non-expired entries

• Single-process only — The store is not shared across processes or servers. Rate limits reset when the process restarts.
• 10,000 entry cap — When the store reaches capacity, it first evicts expired entries. If no entries have expired and the store is still full, new keys are rejected (the attempt call still returns a result with allowed: false).
• Periodic cleanup — A background interval runs every 60 seconds to remove expired entries, preventing memory leaks from accumulated stale data.

import { createRateLimiter, MemoryRateLimitStore } from 'ideal-auth';

// Explicitly passing the default store
const store = new MemoryRateLimitStore();

const limiter = createRateLimiter({
  maxAttempts: 10,
  windowMs: 60_000,
  store,
});

---

RateLimitStore interface

interface RateLimitStore {
  increment(
    key: string,
    windowMs: number,
  ): Promise<{ count: number; resetAt: Date }>;
  reset(key: string): Promise<void>;
}

Implement this interface to use a custom backing store (Redis, database, etc.) for rate limiting in multi-process or distributed environments.

Method	Description
increment(key, windowMs)	Increment the attempt count for key. If the key does not exist, initialize it with a count of 1 and a resetAt time of Date.now() + windowMs. Return the current count and reset time.
reset(key)	Remove the rate limit entry for key.

---

Custom store: Redis example

import { createRateLimiter } from 'ideal-auth';
import type { RateLimitStore } from 'ideal-auth';
import Redis from 'ioredis';

const redis = new Redis(process.env.REDIS_URL!);

const redisStore: RateLimitStore = {
  async increment(key: string, windowMs: number) {
    const redisKey = `rate_limit:${key}`;

    const count = await redis.incr(redisKey);

    if (count === 1) {
      // First attempt — set the expiry
      await redis.pexpire(redisKey, windowMs);
    }

    const ttl = await redis.pttl(redisKey);
    const resetAt = new Date(Date.now() + Math.max(ttl, 0));

    return { count, resetAt };
  },

  async reset(key: string) {
    await redis.del(`rate_limit:${key}`);
  },
};

const loginLimiter = createRateLimiter({
  maxAttempts: 5,
  windowMs: 15 * 60 * 1000,
  store: redisStore,
});

---

Full example: protecting a login endpoint

import { createAuth, createHash, createRateLimiter } from 'ideal-auth';

const hash = createHash();

const auth = createAuth({
  secret: process.env.AUTH_SECRET!,
  cookie: cookieBridge,
  resolveUser: async (id) => db.user.findUnique({ where: { id } }),
  resolveUserByCredentials: async (creds) =>
    db.user.findUnique({ where: { email: creds.email } }),
  hash,
});

const loginLimiter = createRateLimiter({
  maxAttempts: 5,
  windowMs: 15 * 60 * 1000, // 15 minutes
});

async function login(email: string, password: string) {
  // Check rate limit before attempting login
  const limit = await loginLimiter.attempt(email);

  if (!limit.allowed) {
    return {
      error: 'Too many login attempts. Please try again later.',
      retryAfter: limit.resetAt,
    };
  }

  const success = await auth().attempt({ email, password });

  if (!success) {
    return {
      error: 'Invalid email or password.',
      remaining: limit.remaining,
    };
  }

  // Clear rate limit on successful login
  await loginLimiter.reset(email);

  return { success: true };
}

---

Types

import type {
  RateLimiterConfig,
  RateLimitResult,
  RateLimitStore,
} from 'ideal-auth';