Backend & systems·Deployment, release and rollback
one instance behaves differently from the others and nobody can say what was changed on it by hand eight months ago.
Configuration drift
Also calledsnowflake server
Divergence between the intended configuration and what is actually running, accumulated through manual fixes. It produces failures that reproduce on one node only and cannot be tested for. Infrastructure as code plus immutable deploys remove it by making the running state disposable.