Deployment, release and rollback

you put the new build on the servers, which is a completely separate event from anybody actually using the new behaviour.

Deployment

you flip the flag and users start getting the new behaviour, on code that has already been running in production for a week.

Release

you replace the instances a few at a time, so for ten minutes half the fleet is on the old version and half on the new.

Rolling update

you ship in the middle of the afternoon and no request fails, because nothing is ever stopped while it is still serving.

Zero-downtime deployment

you stand up a complete second environment on the new version and switch all traffic to it at once.

Blue-green deployment

you send a copy of real production traffic at the new service and throw the responses away, just to see if it holds up.

Dark launch

you ship the code turned off, switch it on for yourself, then for one percent, then for everyone.

Feature flag

you leave the new version running on ten percent of traffic for an hour before proceeding, because some failures only show up slowly.

Bake time

the deploy broke something so you put the previous version back rather than trying to fix forward under pressure.

Rollback

you cannot go back because the migration already ran, so the only way out is to ship another change quickly.

Roll forward

you add the new column, write to both, backfill, switch reads, and only remove the old one in a later deploy.

Expand and contract

you change the load balancer by editing a file and opening a pull request, not by clicking around in a console.

Infrastructure as code

you never patch a running server; you build a new image and replace the instance entirely.

Immutable infrastructure

one instance behaves differently from the others and nobody can say what was changed on it by hand eight months ago.

Configuration drift

you get mutual TLS, retries and per-route traffic splitting without changing a line of application code, because a proxy sits next to each instance.

Service mesh