Understand the existing system
Identify critical user journeys, integrations, data ownership, and undocumented dependencies. Establish the maintenance, performance, and delivery constraints that modernization needs to resolve.
Change bounded capabilities
Preserve stable interfaces and replace capabilities in manageable stages. Document dependencies and test the important business workflows. Include rollback and operating instructions with each release.
Assess progress against a baseline
Compare representative task latency, deployment effort, support volume, and reliability with the original system. Agree the measurement period, acceptance criteria, and ownership before implementation.