This is a Redis rate limiting demo for JS and Node using:

• Redis Cloud
• Express
• Handlebars + HTMX

NOTE: Read the tutorial on rate limiters for a guide.

Rate Limiting Algorithms

This demo implements five rate limiting algorithms, each backed by different Redis data structures:

Algorithm	Redis Data Structure	Description
Fixed Window Counter	STRING (INCR + EXPIRE)	Counts requests in fixed time windows. Simple but susceptible to boundary bursts.
Sliding Window Log	SORTED SET (ZADD + ZREMRANGEBYSCORE)	Logs each request timestamp. Precise sliding window, but stores every request.
Sliding Window Counter	STRING x2 (weighted)	Weighted average of current and previous window counts. Smooths the fixed-window boundary problem.
Token Bucket	HASH + Lua script	Tokens refill at a steady rate; each request consumes one. Allows short bursts.
Leaky Bucket	HASH + Lua script	Requests fill a bucket that leaks at a constant rate. Smooths traffic to steady output (shaping), or drops requests above the bucket size (policing).

Requirements

• bun
• docker
  • Optional

Getting started

Copy and edit the .env file:

cp .env.example .env

Your .env file should contain the connection string you copied from Redis Cloud.

Your .env.docker file will look similar to .env, but should use the appropriate docker internal URLs. Here is an example:

REDIS_URL="redis://redis:6379"

Next, spin up docker containers:

bun docker

You should have a server running on http://localhost:<port> where the port is set in your .env file (default is 8080).

Open http://localhost:8080 in your browser to see the demo UI. Each rate limiting algorithm has a card with:

• Send Request -- sends a single request through the rate limiter
• Burst 10 -- sends 10 rapid requests to see the algorithm hit its limit
• Reset All Counters -- clears all rate-limit keys from Redis

API Routes

1. POST /api/rate-limit/:algorithm -- Test a single request against the named algorithm
2. POST /api/rate-limit/:algorithm/burst -- Send 10 rapid requests against the named algorithm
3. POST /api/rate-limit/reset -- Reset all rate-limit counters

Where :algorithm is one of: fixed-window, sliding-window-log, sliding-window-counter, token-bucket, leaky-bucket.

Running tests

There are some tests in the __tests__ folder that can be run with the following command:

bun test

These tests setup and teardown on their own. You can modify them if you want to leave data in Redis.

Running locally outside docker

To run the development server outside of docker:

bun install
# then
bun dev

Other Scripts

Formatting code:

bun format

Updating dependencies:

bun update

Connecting to Redis Cloud

If you don't yet have a database setup in Redis Cloud get started here for free.

Then follow the Connect to a Redis Cloud database doc. You should end up with a connection string that looks like the string below:

REDIS_URL="redis://default:<password>@redis-#####.c###.us-west-2-#.ec2.redns.redis-cloud.com:#####"

Run the tests to verify that you are connected properly.

Learn more

To learn more about Redis, take a look at the following resources:

• Redis Documentation - learn about Redis products, features, and commands.
• Redis Tutorials - read tutorials, quick starts, and how-to guides for Redis.
• Redis Demo Center - watch short, technical videos about Redis products and features.