Our daily signals disagreed with the exchange chart, and intraday signals appeared and disappeared within the same bar. We resampled UTC millisecond timestamps in local time and included the still-forming last candle. UTC everywhere and using only closed candles fixed both problems.
A practical guide to time handling that survives DST switches: when to store UTC instants, when to keep local time plus an IANA zone, how gaps and overlaps behave, which database types to use, and how to test with fixed clocks.
Our monthly-partitioned orders table was supposed to make the daily report touch one partition. EXPLAIN showed all 36. A date cast on the partition key and a join-driven filter were blocking pruning, and two small query rewrites brought it back.
On November 3, 2024, our 01:30 billing run fired at 01:30 CDT and again at 01:30 CST, charging 1,284 subscriptions twice. The in-house scheduler matched local wall-clock time. We moved schedules to UTC and added idempotency keys, a run ledger and a unique constraint.