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System design and architecture · Proficient · Lesson 60 of 98 · 2 h 5 min video, then about 4 hours of practice
Scaling fundamentals: load balancing, statelessness and caching
After this you can explain how a single-server application evolves to handle more traffic, and where caches and load balancers fit.
Why it matters
Most systems never need exotic architecture. They need the basics done well: stateless application servers behind a load balancer, a database that is indexed properly, caches in the right places with a clear invalidation strategy, and a CDN for static content. Focus on why statelessness makes horizontal scaling easy, the caching patterns (cache-aside, write-through) and the hard part of caching, which is invalidation. Trap: adding a cache to hide a missing database index.
How to use this resource
Watch 0:00–0:31:01: single server, databases, vertical and horizontal scaling, load balancing, health checks and single points of failure.