Performance
5 pieces of work and writing on this site touch performance.
Case studyPayment Distribution Engine30–40 min → 6–8 min per cycleCase studyEnterprise Desktop App — Startup and Size30–40 s → 5–10 s startup, 25–30% smallerDecisionWhy group batch work by card hierarchy instead of by arbitrary chunks?Because grouping by hierarchy removes duplicated work; chunking arbitrarily only redistributes it.DecisionHow do you query a billion-row transaction table without falling over?Bound every access by a key range, keep the access path matched to an existing index, and stop treating COUNT(*) as free.JournalWhen Parallel Streams Become a Production ProblemparallelStream() is one call away and looks like free concurrency. On I/O-bound work sharing a JVM-wide pool, it is a way to make unrelated code slow.