A scan checks the public surface
An automated security scan inspects what is reachable from a URL: API keys in the client bundle, missing security headers, wildcard CORS, guessable routes, runtime errors, and known vulnerable dependencies. It runs in seconds and is the right first filter.
A review checks the logic behind it
A human review reads the actual code, database policies, secrets, and hosting. It finds access-control flaws, broken authorization, missing Row Level Security, and unsafe workflows that no scanner can detect because they depend on intent, not patterns.
Together they cover launch risk
The scan removes obvious issues cheaply. The review confirms that private data is protected, payments fail safely, and a bad deploy can be rolled back. For an app handling real users, both are needed before launch.