Platform Migrations: Free Product Manager Template

For a typical B2B SaaS product with 100K-1M users: 6-18 months depending on system complexity and team size. A rule of thumb: estimate conservatively, then add 50%. Platform migrations almost always take longer than planned because of edge cases discovered during data migration, integration compatibility issues, and the need to keep the old system running while building the new one. Short migrations (under 6 months) are possible for small systems with few integrations.

Phased, almost always. Big bang migrations are appropriate only for small systems with few users and no external integrations. For anything with paying customers or third-party integrations, phased migration (strangler fig or incremental rollout) reduces risk significantly. The cost is longer duration and the complexity of running two systems simultaneously.

API versioning plus a compatibility layer. Keep v1 endpoints functional by proxying requests to the new system and translating responses to match the old format. Set a deprecation timeline (minimum 12 months) and track v1 usage. Provide migration guides and SDKs that abstract version differences. The [developer ecosystem template](/templates/developer-ecosystem-template) covers API versioning strategy in depth.

Data migration. Application code can be rewritten, APIs can be versioned, and infrastructure can be scaled. But data loss or corruption is often irreversible. Invest disproportionately in data migration planning: schema mapping, validation checksums, dry runs, and rollback procedures. Run at least three full dry runs before the real migration.

Frame it in business terms, not technical terms. "We need to re-architect our system" gets less traction than "Our largest enterprise deal ($400K ARR) requires a public API that our current system cannot support, and our deploy frequency has dropped from daily to weekly, costing us 2 weeks per quarter in delayed feature delivery." Attach specific revenue at risk, opportunity cost, and the [total addressable market](/glossary/total-addressable-market-tam) that the new platform opens up. ---