Deploying and releasing can be two different moments. That is the main idea of the next four words.
Feature flag
Also called Feature toggle, Kill switch, Percentage rollout
A condition in your code that turns something on or off, for some or all users, without a deploy. The code ships switched off, and you switch it on when you are ready.
If a release goes wrong, turning it off takes seconds and not a rollback. A percentage lets you try it on a few people first. The cost is real: each flag is a second version of your code, which has to be tested and later removed.
Say it to your agent
“Put the new checkout behind a flag called new-checkout, off by default, with a hash of the user id picking the percentage, so nobody flips between versions. Test it both on and off. Add a ticket, with an owner, to delete the flag within two weeks of reaching 100%.”