Local Engine

The Local engine stores rate limit state in memory using JavaScript Map objects. It has zero external dependencies and provides sub-millisecond latency.

Installation

npm install @ratelock/local

Quick Start

import { fixedWindow, slidingWindow, tokenBucket, individualFixedWindow } from '@ratelock/local'

const limiter = await fixedWindow({
    limit: 100,
    windowMs: 60_000,
})

const result = await limiter.check('user:123')

All Strategies

Function	Strategy
`fixedWindow`	Fixed Window
`slidingWindow`	Sliding Window
`tokenBucket`	Token Bucket
`individualFixedWindow`	Individual Fixed Window

Configuration Options

All limiters in the Local engine accept these shared base options:

Prop

Type

Strategy-specific options are documented in the Strategies section.

Built-in Resilience Policies

All limiters accept optional resilience configurations at creation time:

const limiter = await fixedWindow({
    limit: 100,
    windowMs: 60_000,
    // Built-in resilience policies (configured at creation time)
    retry: { maxAttempts: 3 },
    fallback: 'allow', // fallback to allow if the limiter errors
})

Option	Type	Description
`retry`	`RetryConfig`	Retry transient failures with exponential backoff
`circuitBreaker`	`CircuitBreakerConfig`	Stop calling after consecutive failures
`fallback`	`'throw' \| 'allow' \| 'deny'`	Behavior when the limiter throws

Note

cache is not supported on the Local engine. There is no network latency to cache.

Standalone Policies (Advanced)

For advanced use cases, import standalone resilience wrappers directly:

import { withFallback, withRetry } from '@ratelock/local'

const limiter = await fixedWindow({ limit: 100, windowMs: 60_000 })
const withResilience = withFallback(withRetry(limiter, { maxAttempts: 3 }), 'allow')

See Resilience Policies for full documentation and when to use standalone vs built-in.

API Reference

The factory functions accept these configuration types:

FixedWindowLimiterConfig