Long-running migration locks table: pre-release and first 30 minutes checklists

A migration takes a lock on a hot table and blocks writes during the deploy window.

The pre-release checklist maps each item to a test class from the incident page. The first-30-minutes checklist covers detection, containment, the rollback decision and customer communication.

7 pre-release items · 7 first-30-minutes items · verified 2026-10-21

Pre-release checklist

PR-01Run the migration against a copy of the production table at full row count and record whether the engine performs the change in place or copies the table. migration
PR-02Set an explicit lock mode and algorithm on every ALTER statement so that the migration fails instead of falling back to a table copy. migration
PR-03Set a lock wait timeout on the migration session so that a pending metadata lock gives up instead of queueing every other query on the table. migration
PR-04Check for open transactions and long-running SELECT statements on the target table immediately before the ALTER starts. migration
PR-05Schedule column drops and foreign key changes outside the windows when worker jobs hold locks on the same tables. migration
PR-06Apply the migration while a load test writes to the target table and confirm the connection pool stays below its limit. load
PR-07Reserve a separate share of database connections for authentication queries and confirm in the load test that login still succeeds while the migrated table is locked. load

First 30 minutes

FM-01Compare the start time of the error rise with the start time of the latest schema migration in the deploy log.
FM-02List the database process table and identify the ALTER statement, the long-running query ahead of it and the queries waiting on the table lock.
FM-03Kill the long-running query that the ALTER is waiting on, or kill the ALTER itself if the table copy will not finish within minutes.
FM-04Terminate blocked writes on the locked table to free connections for other workloads.
FM-05Fail over the database if responders cannot log in with elevated privileges to kill sessions.
FM-06Decide whether to re-apply the migration later or revert it, based on whether the ALTER completed or was killed.
FM-07Post a status update naming the affected surfaces, such as login, API and web interface, and the time the lock started.

Download the checklist

Pre-release checklist (Markdown)1.5 KB · v1.0.0
First 30 minutes checklist (Markdown)1.2 KB · v1.0.0

Only in this checklist

Every test class in this checklist also appears in at least one sibling checklist in the group; the item texts differ: Run the migration against a copy of the production table at full row count and record whether the engine performs the change in place or copies the table.

Questions

What should be checked before a release to prevent Long-running migration locks table?

7 pre-release items, PR-01 to PR-07. PR-01: Run the migration against a copy of the production table at full row count and record whether the engine performs the change in place or copies the table.

Is there a rollback plan for Long-running migration locks table?

The first-30-minutes checklist has 7 items. FM-01: Compare the start time of the error rise with the start time of the latest schema migration in the deploy log.

What should a team do in the first 30 minutes after Long-running migration locks table is detected?

The first-30-minutes checklist has 7 items. FM-01: Compare the start time of the error rise with the start time of the latest schema migration in the deploy log.

Is a Long-running migration locks table checklist still needed if deployment is automated?

Yes. Automation runs the steps; the checklist names what the tests must cover: migration tests and load and performance tests.

Which pipeline stages does the Long-running migration locks table checklist cover?

The pre-release items map to the pre-deploy stages.

In what formats can the Long-running migration locks table checklist be downloaded?

Both checklists download as Markdown files: /downloads/long-running-migration-locks-table-pre-release.md and /downloads/long-running-migration-locks-table-first-30-minutes.md, licensed CC BY 4.0.