Throttling vs Rate limiting in APIs

• When your API becomes popular, you need to protect it from being overwhelmed by too many requests. This is where throttling and rate limiting come in. While these terms are often used interchangeably, they serve different purposes in API management.

• Rate limiting is like setting a hard limit on the number of requests a client can make in a specific time window. For example, you might allow each user to make 100 requests per hour. Once a user hits this limit, their requests are rejected until the next hour begins. Rate limiting is straightforward to implement and understand, making it a common choice for simple API protection.

• Throttling takes a more flexible approach. Instead of outright rejecting requests, throttling slows down the rate at which requests are processed when the system is under heavy load. Think of it as a "soft limit" that adapts to current conditions. When the system is busy, requests might be delayed or queued rather than rejected.

• For example, if your API normally handles 1000 requests per second but suddenly receives 2000 requests per second, throttling might slow down the processing rate to maintain system stability. This is particularly useful during traffic spikes or when you want to ensure fair resource distribution among users.

• Both approaches have their place in API management. Rate limiting works well when you need strict control over resource usage, like in freemium models where different subscription tiers get different request limits. Throttling is better when you want to maintain service availability during unexpected traffic spikes.

Here's a comparison of the two approaches: