@krishnachaytanya: Zero-downtime database migration: how you change a live table while users are still hitting it. Run ALTER TABLE to change a column type and Postgres locks the whole table. Every query waits. That is your downtime. So instead of editing the track under a moving train, you build a new one beside it: EXPAND: add the new column BACKFILL: copy old rows over in batches SWITCH: flip reads to the new column mid-flight (writes go to both during the overlap) CONTRACT: drop the old column The train never stops. 0 queries dropped. Postgres, plus GitHub's gh-ost and Stripe, migrate exactly this way. Save this for your next schema change. Which step trips people up most: the backfill or the switch? #systemdesign #database #postgres #backend #softwareengineering

KrishnaChaitanya|SystemDesign

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Friday 04 September 2026 12:59:41 GMT