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Series
Most system design content jumps straight to designing the next big platform — and skips the building blocks that actually make those designs possible. This blog series fixes that: one core concept per post — hashing, partitioning, replication, consistency, caching — broken down from first principles until it genuinely clicks. Because the difference between recalling an answer and actually understanding one shows up the moment someone asks why.
Part 1: The Comfort of Vertical Scaling Picture this. You've built an e-commerce backend on PostgreSQL. Everything is on a single server — one instance, one disk, one brain making all the decisions. F
The problem consistent hashing solves Say you shard your users table across 4 database nodes /shards using a hash function -> hash(user_id) % 4. This works fine — until you add a 5th node. Now % 4 bec
