$ sudo explain --topic anything
The why behind the tech, explained clearly.
Sudo Explain is an engineer's notebook on core concepts, system design and production failures, written to answer the questions that tripped me up.
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9 min read
Idempotency key: stop a retry from charging twice
A timeout and a retry can charge a customer twice. See how to find the duplicate and how an idempotency key makes a retry safe.
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11 min read
Java memory leak: strong references and heap dumps
Java has a garbage collector, yet services die with OutOfMemoryError. How strong references cause leaks, how to find them in a heap dump, and the fixes.
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13 min read
HikariPool-1 Connection is not available: pool exhausted
Why a Java app hangs with Connection is not available errors under load, how leaked or hoarded connections cause it, and how to find and fix it.
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13 min read
Slow SQL query: find a missing index with EXPLAIN
Your SQL query was fast in testing but takes seconds in production. Find out why, how to read EXPLAIN, and how to add an index that works.
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15 min read
N+1 query problem in Hibernate and JPA: find it and fix it
Why a Hibernate or JPA page that is fast in development takes 10 seconds in production, how lazy loading hides hundreds of queries, and how to fix it.
