What Are API Rate Limits and How Do They Work?

With 12+ years specializing in database systems and backend engineering, when I built my first production API in 2014, I didn’t implement rate limiting. Within two weeks, a poorly written client script made 47 million requests in a single day, crashing our database and costing us $8,000 in emergency infrastructure scaling. I learned about rate limiting the hard way. After spending a decade designing and implementing APIs for startups and enterprises, including systems serving 2 billion+ requests daily, I’ve developed a deep understanding of why and how rate limiting protects both API providers and consumers. This comprehensive guide explains rate limiting mechanisms, implementation strategies, and best practices from real-world experience.