What deployment strategies are there and what are they used for?

Deployment strategies are methods of releasing new versions of applications or services that help minimize downtime, risks, and ensure stability. Main strategies:

• Blue-Green Deployment: two identical environments (blue and green). The new version is deployed in the inactive environment, and after testing, traffic is switched to it. Allows quick rollback.

• Canary Deployment: the new version is launched on a small number of servers or for a small portion of users. If everything is stable, the traffic share gradually increases.

• Rolling Deployment: the update occurs gradually, with servers switching to the new version one by one, without stopping the entire service.

• Recreate Deployment: the old version is completely stopped, then the new one is launched. Downtime, but with service downtime.

• A/B Testing: similar to canary, but aimed at testing different versions for user behavior analysis.

The choice of strategy depends on requirements for availability, risks, and infrastructure.