databases
19 minDatabase Internals Advanced: MVCC Anomalies, Cost Models, Sharding, and Storage Engines
Reason about isolation anomalies, query-plan mistakes, B-tree/LSM trade-offs, shard routing, and production-safe index changes.
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4 matching resultsArticles and interview answers
Q&A
Q&AWhy can a long PostgreSQL transaction delay vacuum cleanup?
An old transaction snapshot may still need row versions that newer transactions have replaced.
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PostgreSQL MVCC keeps row versions visible to active snapshots. A long-running transaction can hold an old snapshot open, so vacuum cannot yet remove some dead versions. Bound transaction lifetimes and investigate idle-in-transaction sessions when table bloat grows.
devops
10 minDocker Multi-Stage Builds: Optimization Patterns for Production
Multi-stage builds keep the runtime image lean while preserving a fast developer loop. Learn how to separate build dependencies from runtime dependencies without losing traceability or reproducibility.
Q&A
Q&AWhat property should a reduce operation have for safe parallel combination?
Associativity and an identity element make regrouping partial results meaningful.
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A parallel reduction may group values differently, so its combine operation should be associative for equivalent results and have a suitable identity value. Floating-point addition can vary slightly with grouping. Avoid reducers with hidden side effects because execution order may not be stable.