A guided route from the basics to senior system-design fluency. Each step is a real simulator you operate β work top to bottom, or jump anywhere.
How the web works before any database or cluster.
Request/response, status codes, caching, REST vs RPC vs GraphQL.
Interleaving on one core vs real overlap on many; speedup and Amdahl's law.
Latency hierarchy, throughput, Little's Law, and nines β downtime.
The structures the rest of the stack is built on.
How databases actually persist and find data on disk.
Make reads fast β and keep the cache honest.
cache-aside, write-through/back/around, TTL, stampede.
Concurrency and traffic control on a single node.
Spread data across machines and find it again.
The ring that moves minimal data when nodes change.
XOR distance + k-buckets; O(log n) lookups, no coordinator.
Round-robin, least-conn, weighted, power-of-two-choices.
Keep copies in sync when clocks and networks lie.
Why clocks drift and how NTP-style sync corrects them.
Epidemic dissemination / anti-entropy with no coordinator.
Make many services agree β or undo together.
Atomic commit across services β and its blocking flaw.
Multi-service transactions via compensating rollback.
Decouple producers from consumers with a durable log.
Partitioned log: consumer groups, offsets, rebalancing.
Trade a little accuracy for a lot of memory.