January 22, 2025 · Faith Forge Labs Editorial Team
From a Monolith to Services: Decide What Actually Needs to Move
Splitting an application into services adds operating work as well as flexibility. Start with the specific release, reliability or scaling problem that needs solving.
A monolith is an application whose main parts are released together. It can be a sensible design. Teams usually consider splitting it into services because releases interfere with each other, a workload needs different capacity or one part has become difficult to change.
Those problems deserve investigation before a migration is chosen. Clearer modules or better release tests inside the existing application may solve them with less disruption.
Understand the current application
Map the important features, data dependencies and release process. Identify where failures occur and how customers experience them. Add enough tests and operational information to recognize a behavior change.
A modular monolith keeps one application while giving its internal parts clearer responsibilities and interfaces. It can improve maintainability without introducing separate deployments and network communication.
Choose a boundary with a practical benefit
A separate service may be useful when a workload needs its own capacity, can be released independently or can fail without interrupting other important tasks. Ask what the separation will improve and how that improvement will be measured.
If two components must change together every time, separating them may add coordination without providing independence. Include the support and deployment effort in that decision.
Decide who owns the data
Putting a network interface between two pieces of code does not resolve shared-data problems. Establish which component is responsible for each record and how others receive updates.
Some operations must be atomic: all related changes succeed together or none do. Other information can tolerate a delay before every part of the system agrees, often called eventual consistency. Define what people see during that delay and how errors are corrected. The term alone does not describe an acceptable customer experience.
Expect incomplete replies and repeated attempts
A remote system can complete work even when its reply is lost. Retrying may repeat the action. Idempotent handling makes repeated requests for the same operation produce one intended change.
Set timeouts and limits on repeated calls. Use a common tracking reference across related steps so support can follow a failure. Decide what happens when queued work builds up or one service is unavailable.
Move one part and assess the result
Start with a limited amount of work and retain a tested recovery route. Compare release effort, reliability, response time and operating cost, including the time people spend supporting the new service.
Ask for the data-ownership rules, deployment and recovery instructions, and the evidence behind the next recommendation. Further separation should follow an observed benefit. Keeping the remaining application together can be the right long-term decision.