Real-world problems
Backend problems with runnable Go prototypes. Pick a bucket to drill.
Coordination
1Many callers, one resource — thundering herd, singleflight, rate-limited fan-in.
Realtime & messaging
0Push channels, pub/sub, persistent connections — WebSockets, NATS, the protocols underneath.
Reliability
0Retries, idempotency, dead-letter queues — making distributed systems survive their own failures.