Monolith

A monolith is an application packaged and deployed as a single unit: one codebase, one build, one process, one database. Everything ships together. Most applications start as monoliths and many remain so for their entire useful life; the term has acquired a pejorative tone in recent years that obscures how often it is the right choice.

Strengths

• Simple operations. One thing to deploy, one set of logs, one stack trace per error.
• Easy local development. Run the whole system on a developer laptop.
• Cross-module refactoring is free. Rename a function and the compiler surfaces every call site to update.
• Strong transactional guarantees. One database, ACID transactions across the whole domain.

Where it strains

• Team coordination. Many teams editing one codebase produces release coordination overhead.
• Heterogeneous tech needs. One module wants Python for ML, another wants Rust for performance; a monolith picks one stack.
• Independent scaling. One hot path forces scaling the whole binary even if other modules are idle.