Rate Limiter

The previous chapters have described the underlying technologies such as consistent hashing, ID generator, and now using these techniques we can develop a URL shortener that can generate 100 million URLs per day.

Design consists of the following elements:

• API endpoints
• URL redirecting
• URL shortening
• Data model
• Hash functions: Hash + collision resolution vs Base-62 conversion
• Additional topics to consider:
  • Rate limiter
  • Web server scaling
  • Database scaling
  • Analytics
  • Availability, consistency, and reliability

These items are disclosed in a very interesting Chapter 8 of the book:

Every popular software should have a Rate Limiter. It prevents DDOS attack, reduces cost and prevents servers from being overloaded.

There are some tricky questions to be considered during implementation of Rate Limiter:

• Where to put Rate Limiter: client-side, server-side, gateway?
• Algorithms for rate limiting. There are many algorithms with pros and cons: Token bucket, Leaking bucket, Fixed window counter, Sliding window log, Sliding window counter. Your business needs will define the right algorithm.
• How are rate limiting rules created?
• Where are the rules stored?
• How to handle requests that are rate limited?

These questions are disclosed in a very interesting Chapter 4 of the book: