4 lessons
Consistent Hashing
The trick that lets you add or remove a server without reshuffling almost all of your data — and why it's the answer behind sharding, load balancers and distributed caches alike.
Replication, Quorums and Consensus
How multiple copies of the same data stay (mostly) in agreement, what a quorum actually buys you, and how a cluster picks a leader without a coin flip.
Reliability Patterns — Timeouts, Retries, Circuit Breakers
Why a slow service is more dangerous than a dead one, and the handful of patterns that stop one failing component from taking down everything connected to it.
Microservices Communication and Observability
Once a system is many services instead of one, you gain independent deployability and lose the ability to see what's happening — here's how you get visibility back.