Case study · Insurance
Legacy Monolith Modernization
Strangler-pattern modernization with domain-driven decomposition.
Key results
- Release frequency +12x
- Production incidents -48%
- Developer onboarding time -60%
Context
A property and casualty insurance carrier ran its core policy-administration system on a Java monolith built over 15 years. The codebase was 2 million lines; releases took weeks; new developer productivity measured in months before meaningful contribution.
Challenge
A big-bang rewrite would have taken 3-5 years with no usable intermediate milestones and high probability of failure. The business needed modernization that delivered value in quarters rather than years while de-risking the long-term exit from the monolith.
Approach
Thoughtwave led an 18-month strangler-pattern modernization: domain-driven decomposition into bounded contexts, new functionality shipped to modern microservices, and existing functionality migrated contextually as each domain's ownership matured. The monolith shrank quarter by quarter; no big-bang cutover was needed.
Outcomes
Release frequency improved 12× as modernized domains shipped independently; production incidents dropped 48% with better testing and observability; developer onboarding time dropped 60% as new developers worked on modern services rather than learning the monolith. The monolith is on track for full retirement over the following 18 months.
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