Decomposing a coupled payment-processor service

Challenge

Processor responsibilities had accumulated in one tightly coupled service, increasing the cost and risk of certification and production changes.

Constraints

• Preserve externally observable behavior during the decomposition.
• Keep callers behind the existing facade while responsibilities moved.
• Improve testability without a broad platform rewrite.

Approach

1. Identified cohesive processor responsibilities and extracted focused modules.
2. Retained a stable facade so callers did not absorb the refactor.
3. Made the extracted responsibilities independently testable.

Outcome

Processor logic became less coupled and independently testable while callers continued to use the stable facade.

My role

Architecture direction, plan-driven decomposition, review, and delivery leadership.