Per-user vs per-IP limits in Rest API - When to Use Which

The Big Idea

What if your website unfairly blocks real users just because they share an internet connection?

The Scenario

Imagine you run a popular website where many people log in and use your services. You want to stop anyone from sending too many requests and slowing down your system. So, you try to limit how many requests come from each IP address manually.

The Problem

But this manual way is tricky because many users can share the same IP (like in offices or cafes), and some users might use different IPs. This causes unfair blocking or lets some users overload your system. It's slow and full of mistakes.

The Solution

Using per-user and per-IP limits together helps you control traffic smartly. You can limit each user's requests no matter where they connect from, and also limit requests from suspicious IPs. This keeps your system fair and safe without blocking good users.

Before vs After

✗ Before

if requests_from_ip > 100:
    block_ip()

✓ After

if requests_from_user > 50:
    block_user()
if requests_from_ip > 100:
    block_ip()

What It Enables

This approach lets you protect your service from overload while treating users fairly, improving reliability and user experience.

Real Life Example

A streaming service limits each logged-in user to 3 devices (per-user limit) and also blocks IPs that send thousands of requests in minutes (per-IP limit) to stop hackers and keep streams smooth.

Key Takeaways

Manual IP-only limits can block many good users sharing one IP.

Per-user limits track individual users regardless of IP changes.

Combining both limits protects systems fairly and effectively.