Posts
All the articles I've posted.
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LeetCode 946 Validate Stack Sequences
Solution for LeetCode 946, medium, tags: array, stack, simulation.
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System Design - How PostgreSQL Index-Only Scans Use the Visibility Map
Why a covering index does not always avoid heap visits: follow one PostgreSQL index-only scan through the visibility map, VACUUM, and EXPLAIN's Heap Fetches counter.
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System Design - How TiDB's UNION ALL Executor Merges Chunks
Trace TiDB's root UnionAllExec from planner to worker goroutines, reusable chunks, error delivery, and the session concurrency knob.
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LeetCode 2574 Left and Right Sum Differences
Solution for LeetCode 2574, easy, tags: array, prefix sum.
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System Design - How Sagas Coordinate Distributed Transactions
Follow an order through inventory reservation, payment, and compensation to understand what a saga guarantees, what it cannot undo, and how to make retries safe.
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System Design - How TiDB's Projection Executor Runs Expressions
Trace a root TiDB Projection from physical plan to child chunks, expression evaluation, and ordered parallel workers; learn why it sometimes runs sequentially.