Migrating APIs

Overview

Implement API migrations between versions, frameworks, or platforms with minimal downtime using strangler fig pattern, parallel running, and traffic shadowing. Generate migration plans that map old endpoints to new equivalents, transform request/response formats, and validate data consistency between legacy and target implementations.

Prerequisites

• Source API codebase and OpenAPI specification accessible for analysis
• Target framework or platform environment provisioned and accessible
• Traffic routing capability for gradual cutover (reverse proxy, feature flags, or API gateway)
• Database migration tools if schema changes accompany the API migration (Flyway, Alembic, Prisma Migrate)
• Integration test suite covering all existing API consumers

Instructions

1. Inventory all existing endpoints using Grep and Read, documenting HTTP methods, URL patterns, request/response schemas, authentication mechanisms, and consumer dependencies.
2. Generate an endpoint mapping table that pairs each legacy endpoint with its target equivalent, flagging breaking changes in URL structure, field names, data types, and authentication flow.
3. Create request/response adapters that transform legacy format to target format, handling field renames, nested-to-flat conversions, and enum value changes.
4. Implement a traffic router (reverse proxy rules or middleware) that directs requests to either the legacy or target implementation based on migration phase, endpoint, or feature flag.