express-quota-limiter

[kfiross]

Just wanted to share I created express-quota-limiter

express-quota-limiter is a flexible, TypeScript-based middleware for Express.js designed specifically for managing long-term quotas (e.g., monthly email limits or daily API allowances) rather than short-term rate limiting.

Core Overview
Purpose: Tracks and enforces usage limits over long windows (days, weeks, months).

Backend Agnostic: Uses a driver-based system. It supports Redis (via ioredis or node-redis) for production and a MemoryDriver for local testing.

Atomic Operations: Prevents race conditions using Redis pipelines, ensuring accurate counting even with concurrent requests.

Key Features
Custom Key Generation: Define how to identify users or tenants (e.g., by User ID, API Key, or IP).

Request Weighting: Assign different "costs" to different requests. For example, a single bulk-upload request can consume 50 units of a quota, while a single fetch consumes only 1.

Dynamic Limits: Supports fetching limits asynchronously (e.g., pulling a user's specific plan limit from a database during the request).

Fail-Open Design: If the storage backend (like Redis) goes down, the middleware allows requests through by default to avoid breaking the application.

Callbacks: Includes hooks like onQuotaChecked and onQuotaExceeded for logging, analytics, or triggering billing alerts.