System design messaging
At-least-once vs exactly-once
Idempotent consumers, dedupe keys, and why exactly-once is a protocol, not a slogan.
Week 2Thursday 17 SeptemberQueues
Day 13: Queues and async
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System design messaging
Competing consumers, poison pills
Visibility timeout, DLQ, retry budget. What you do with a bad payload.
Coding sliding window
Sliding Window Maximum
LC 239. Monotonic deque. Invariant: front is max of the window.
LLD concurrency
Bounded blocking queue
put/take, capacity, notify. Sketch Java/C# monitors or a condition variable.