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Microservices Decision Aid

Score a candidate service against the conditions where microservices succeed and where they fail, so the team makes an evidence-based choice rather than following a trend.

Phase D, Technology ArchitectureDerived from TOGAF

Microservice fit on two axes: independent change and independent failure

The grid encodes the two preconditions for a service boundary on the X and Y axes. Each quadrant names the outcome of one combination and what it still has to carry.

Microservices earn their cost only when a part can change and fail on its own. Mapping those two properties to a quadrant shows where a split pays off and where the monolith is the honest call.

Microservice fit on two axes: independent change and independent failure A matrix of microservice fit on two blue axis rails: a vertical Independent change rail, coupled to free, and a horizontal Independent failure rail, coupled to isolated. Each quadrant pairs a green win marker with an amber cost marker. Coupled change with coupled failure is Keep the monolith: splitting wins nothing. Free change with coupled failure is Split release, shared failure: teams ship on their own cadence but one fault takes the rest down. Coupled change with isolated failure is Shared release, bulkheaded: a fault stays inside but each change ships together. Free change with isolated failure, in red, is Microservice fit: independent change and failure, paid with network and contract. Independent change: coupled to free Independent failure: coupled to isolated Change free, coupled failure Split release, shared failure Teams ship on their own cadence One fault can take the rest down Both properties hold Microservice fit Independent change and failure Network, contracts and observability Neither property holds Keep the monolith No coordination tax, easy to reason about Coupling is real, splitting wins nothing Failure free, coupled change Shared release, bulkheaded A fault stays inside its own boundary Every change still ships together What the combination winsWhat it still has to carry Only the top-right quadrant earns a split.If a part cannot change and fail on its own, the monolith is the honest answer; the partial quadrants needextra controls before they qualify.