Blue/Green Deployments

Steps

• version B (green) is deployed alongside version A (blue) with exactly the same amount of instances.
• After testing traffic is switched from version A to version B at the load balancer level.

It has

• Instant rollout/rollback.
• Avoid versioning issue, the entire application state is changed in one go.
• Expensive as it requires double the resources.
• Proper test of the entire platform should be done before releasing to production.
• Handling stateful applications can be hard.
• can use the primary database by blue for write operations and use the secondary by green for read operations
• During switchover, database is failed over from primary to secondary

Green deployment

Blue deployment