Acquia Cloud Platform Architecture and Environments
Acquia Cloud organizes work into an organization → application → environment hierarchy, and questions love to test which level a setting or artifact lives at. An application groups related code and databases; environments (Dev, Stage, Prod, plus on-demand environments created from a branch or a database backup) are isolated runtime stacks. Each environment has its own code, database, and file system, and each has its own set of servers. A common trap is assuming Prod and Stage share a database or files-they never do; data moves only when you deliberately copy it.
Know the infrastructure tiers: Professional vs Enterprise, single-region vs multi-region (CDN plus failover), and the role of the load balancer, Varnish, and web/DB server split. Acquia Cloud uses Varnish in front of Apache/nginx, so caching is part of the architecture, not an add-on. On-demand environments and non-production environments are billed and behave differently; questions often ask whether a given environment can be resized independently (it can).
Worked rule of thumb: if a question asks "where does this change take effect?" first identify the level-organization (teams, billing, SSO), application (code repo, cron, SSL), or environment (variables, domains, PHP version, server size). Only environment-level changes are isolated; application-level changes propagate to every environment on the next deploy or refresh.
Watch for traps about which environment a database backup restores into (you can restore to any environment, but it overwrites), and about the difference between an environment's primary domain and additional custom domains.