Stop worrying about PostgreSQL locks in your Rails migrations

Doctolib applications are used by more than 135 000 medical practitioners in France and Germany. They receive more than 70 million patient visits per month. At peak time, our Postgres database handles more than 15 000 requests per second. Acting in the healthcare field, reliability is critical for us. A downtime directly impacts the access to healthcare for practitioners and patients.At Doctolib, we write a lot of migrations in our Rails monolith: during the first half of the year 2020, 13 000 pull-requests were merged, in which more than 500 migrations were created and executed against our production database.