The architecture in order
- Start with one server and one database.
35:53 - Add identical app servers and a load balancer when one server cannot handle concurrent traffic.
35:53 - Put sessions in a shared store so those servers remain interchangeable.
35:53 - Pool database connections and send most reads to replicas when the database becomes the bottleneck.
35:53 - Cache repeated expensive answers.
35:5336:22 - Put slow, deferrable work on a queue for background workers.
36:22 - Shard only when the full dataset no longer fits on one machine.
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Final lesson
- Many production applications need no more than the load-balanced, stateless, pooled, replicated, cached, and queued architecture described here.
29:4036:22 - Tools, including AI, can implement the components. Engineering judgment decides which components the product needs and which costs it can accept.
36:22 - In system-design interviews and real projects, naming technologies is not enough. Strong reasoning explains why to choose each one, why to add it at that point, and what tradeoff follows.
36:5937:31