Designs service boundaries using bounded contexts, data ownership, communication patterns, and a migration sequence.
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name: microservices-decomposition
description: "Design a microservices decomposition for a monolith or new system, defining service boundaries, ownership, communication patterns, and migration plan. Use when asked to decompose a monolith, define service boundaries, design a microservices architecture, or plan a strangler-fig migration. Produces a bounded context map, service inventory table, communication pattern decisions, data ownership matrix, migration roadmap, and risk register."
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# Microservices Decomposition
Produce a complete microservices decomposition design for a system — whether decomposing an existing monolith or designing service boundaries for a new system. Ground the decomposition in Domain-Driven Design (DDD) concepts: identify bounded contexts first, then derive service boundaries from them. Include communication pattern decisions (sync vs. async, event vs. RPC), data ownership rules, and a pragmatic migration plan if decomposing a monolith. Conway's Law is real — include an organizational alignment section. The deliverable should be specific enough that a team can begin implementation, not an abstract architectural diagram.
## Required Inputs
Ask for these if not already provided:
- **System or domain description** — what the system does, its core domain, and the key business processes it supports
- **Current architecture** — monolith (describe the tech stack and rough module structure), partial services (list existing services), or greenfield
- **Team structure** — number of teams, team names if known, and approximate team sizes; this drives service ownership
- **Performance and scalability requirements** — any specific SLAs, load characteristics, or scaling constraints per domain area
- **Migration constraints** — what cannot be rewritten all at once, hard deadlines, zero-downtime requirements, budget constraints
- **Integration points** — external systems, third-party APIs, or legacy systems that cannot be changed
If decomposing a monolith, also ask for: approximate codebase size, what is most painful to change today, and where the team experiences the most coupling-related friction.
## Output Format
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