Intro

Architecture is about structuring software so it can evolve: clear boundaries, explicit tradeoffs, and sustainable complexity. Good architecture makes the “next change” cheaper without over-engineering the current one. Example: choosing between a modular monolith and microservices is mainly about team boundaries, deployment independence, and operational cost.

Questions

How do you choose between a monolith, a modular monolith, and microservices?

• The decision is mainly organizational: microservices buy independent deployment and team autonomy at the cost of network calls, distributed failure modes, and operational overhead
• A modular monolith captures most of the boundary benefits — clear module seams, enforced dependencies — while keeping one deployable and in-process calls; it’s the right default for most teams
• Reach for microservices when independent scaling or deployment or team boundaries genuinely demand it, not because it’s fashionable, and rarely before you understand the domain boundaries
• Migration is one-directional and cheap the right way round: a well-structured modular monolith can later be carved into services along its existing seams

References

• Architecture styles (Microsoft Azure Architecture Center) — a decision-oriented survey of monolith, microservices, event-driven, and other styles.
• Patterns of Enterprise Application Architecture (Martin Fowler) — the canonical catalog of application-architecture patterns.
• Fallacies of distributed computing (Wikipedia) — the assumptions that break every distributed architecture; essential before splitting a system.