Decompose a monolith when specific constraints justify it, such as independent deployment, ownership boundaries, or uneven resource demand. Record the current bottleneck and evaluate whether a modular monolith would resolve it first. More services also introduce communication, consistency, and operational costs.
The migration pattern we recommend starts with the Strangler Fig approach. You identify bounded contexts within the existing monolith — domains with high change frequency, independent scaling requirements, or distinct data ownership. These become the first extraction candidates. The monolith continues handling everything else while you incrementally route traffic through the new services.
Domain events can decouple consumers from a producer, but reliable publication needs an explicit contract. Account for duplicates, ordering, schema changes, and consumer recovery. An event log supports selected replay scenarios; restoring a system also requires databases, configuration, dependencies, and a tested recovery procedure.
Select orchestration, messaging, storage, and network controls according to workload and team capability. Managed containers, a conventional application server, or Kubernetes can each be appropriate. Do not add a service mesh or event platform without a concrete requirement and an operational owner.
Use structured logs, relevant metrics, and traces where they help explain cross-service behavior. Define actionable alerts and avoid retaining secrets or unnecessary customer content. Verify observability coverage on the critical workflow instead of claiming that every service is already instrumented.
Service-owned data can support independent changes, but cross-service operations need deliberate consistency rules. A saga uses compensating business actions where feasible; compensation is not equivalent to rolling back one database transaction and may itself require recovery.
Evaluate a migration using deployment lead time, recovery drills, error rates, and workload-specific resource measurements. Preserve the baseline and explain tradeoffs. Without documented before-and-after evidence, describe the architecture and acceptance checks rather than attributing traffic or recovery improvements to a client.
