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+---
+description: Migrate API to new version with compatibility layers and automated scripts
+shortcut: migrate
+---
+
+# Migrate API Version
+
+Orchestrate comprehensive API version migrations with automated compatibility layers, breaking change detection, and zero-downtime deployment strategies. This command manages the complete lifecycle of API evolution from initial analysis through deployment and deprecation.
+
+## Design Decisions
+
+**Architecture Approach:**
+- Version routing at API gateway level for clean separation
+- Adapter pattern for backward compatibility transformations
+- Feature flags for gradual rollout control
+- Automated test generation across all supported versions
+
+**Alternatives Considered:**
+- Hard cutover migration (rejected: high risk, no rollback)
+- Separate API endpoints per version (rejected: operational complexity)
+- GraphQL federation (chosen for microservices architectures)
+- BFF pattern for client-specific migrations
+
+## When to Use
+
+**USE when:**
+- Introducing breaking changes to API contracts
+- Deprecating legacy endpoints with controlled timelines
+- Migrating between API paradigms (REST to GraphQL)
+- Evolving data models with backward incompatible changes
+- Implementing new authentication mechanisms
+- Consolidating multiple API versions
+
+**DON'T USE when:**
+- Adding backward-compatible endpoints (use versioned routes)
+- Making internal refactoring without contract changes
+- Deploying hotfixes or security patches
+- Changes affect only implementation, not interface
+
+## Prerequisites
+
+**Required:**
+- Complete OpenAPI/GraphQL schema for both versions
+- Comprehensive API test suite with >80% coverage
+- Version control with tagged releases
+- Deployment pipeline with rollback capability
+- API gateway with routing rules support
+- Monitoring and alerting infrastructure
+
+**Recommended:**
+- Consumer registry with contact information
+- Deprecation policy documented and communicated
+- Traffic analysis showing endpoint usage patterns
+- Backward compatibility test matrix
+- Canary deployment environment
+
+## Migration Process
+
+**Step 1: Analysis and Impact Assessment**
+- Scan API schemas to detect breaking changes
+- Analyze usage patterns from API logs
+- Identify affected consumers and endpoints
+- Calculate complexity score for migration effort
+- Generate compatibility matrix between versions
+
+**Step 2: Compatibility Layer Generation**
+- Create adapter functions for data transformation
+- Generate request/response mappers automatically
+- Build version-specific validation schemas
+- Implement fallback logic for missing fields
+- Create deprecation warning middleware
+
+**Step 3: Migration Script Creation**
+- Generate database migration scripts for schema changes
+- Create data backfill scripts for new required fields
+- Build rollback procedures for each migration step
+- Generate test fixtures for both API versions
+- Create automated smoke tests for critical paths
+
+**Step 4: Routing and Deployment Configuration**
+- Configure API gateway version routing rules
+- Set up feature flags for gradual rollout
+- Implement traffic splitting for canary deployment
+- Configure monitoring dashboards for version metrics
+- Set up deprecation warning headers and logs
+
+**Step 5: Validation and Monitoring**
+- Execute automated test suite across all versions
+- Verify backward compatibility with consumer tests
+- Monitor error rates and performance metrics
+- Track adoption rates for new version
+- Schedule deprecation timeline communications
+
+## Output Format
+
+```yaml
+migration_plan:
+  api_name: "User Service API"
+  source_version: "v1"
+  target_version: "v2"
+  breaking_changes:
+    - endpoint: "/users"
+      change_type: "field_removed"
+      field: "username"
+      severity: "high"
+      affected_consumers: 15
+    - endpoint: "/users/{id}"
+      change_type: "response_structure"
+      details: "Nested address object"
+      severity: "medium"
+      affected_consumers: 8
+
+  compatibility_layer:
+    adapters_generated: 12
+    transformation_functions: 8
+    fallback_strategies: 5
+
+  migration_scripts:
+    - script: "001_add_email_unique_constraint.sql"
+      type: "database"
+      rollback: "001_rollback_email_constraint.sql"
+    - script: "002_backfill_address_objects.js"
+      type: "data_transformation"
+      estimated_time: "15 minutes"
+
+  deployment_strategy:
+    type: "canary"
+    phases:
+      - name: "internal_testing"
+        traffic_percentage: 0
+        duration: "3 days"
+      - name: "early_adopters"
+        traffic_percentage: 10
+        duration: "1 week"
+      - name: "general_rollout"
+        traffic_percentage: 100
+        duration: "2 weeks"
+
+  deprecation_timeline:
+    warning_start: "2024-01-01"
+    support_end: "2024-06-30"
+    sunset_date: "2024-12-31"
+    notification_plan: "Email + dashboard banner"
+
+  monitoring:
+    dashboards:
+      - "API Version Adoption Metrics"
+      - "Error Rate by Version"
+      - "Response Time Comparison"
+    alerts:
+      - "V2 error rate > 5%"
+      - "V1 traffic spike (rollback indicator)"
+```
+
+## Code Examples
+
+### Example 1: REST API v1 to v2 Migration with Breaking Changes
+
+```javascript
+// API v1 → v2 Migration: User endpoint restructure
+// BREAKING: Flattened user object to nested structure
+
+// Source: /api/v1/users/{id}
+{
+  "id": 123,
+  "name": "John Doe",
+  "email": "john@example.com",
+  "street": "123 Main St",
+  "city": "San Francisco",
+  "state": "CA",
+  "zip": "94105"
+}
+
+// Target: /api/v2/users/{id}
+{
+  "id": 123,
+  "name": "John Doe",
+  "email": "john@example.com",
+  "address": {
+    "street": "123 Main St",
+    "city": "San Francisco",
+    "state": "CA",
+    "postalCode": "94105"
+  },
+  "metadata": {
+    "createdAt": "2024-01-15T10:30:00Z",
+    "version": "v2"
+  }
+}
+
+// Generated Compatibility Adapter
+class UserV1ToV2Adapter {
+  transform(v1Response) {
+    return {
+      id: v1Response.id,
+      name: v1Response.name,
+      email: v1Response.email,
+      address: {
+        street: v1Response.street,
+        city: v1Response.city,
+        state: v1Response.state,
+        postalCode: v1Response.zip // Field renamed
+      },
+      metadata: {
+        createdAt: v1Response.created_at || new Date().toISOString(),
+        version: "v2"
+      }
+    };
+  }
+
+  reverseTransform(v2Response) {
+    // For backward compatibility when v1 clients hit v2
+    return {
+      id: v2Response.id,
+      name: v2Response.name,
+      email: v2Response.email,
+      street: v2Response.address?.street || "",
+      city: v2Response.address?.city || "",
+      state: v2Response.address?.state || "",
+      zip: v2Response.address?.postalCode || ""
+    };
+  }
+}
+
+// API Gateway Routing Configuration
+const routingRules = {
+  "/api/v1/users/:id": {
+    target: "/api/v2/users/:id",
+    adapter: "UserV1ToV2Adapter",
+    deprecationWarning: {
+      header: "Deprecation",
+      value: "API v1 will be sunset on 2024-12-31. Migrate to v2.",
+      link: "https://docs.example.com/api-migration"
+    }
+  }
+};
+
+// Migration Script: Database Schema Evolution
+// 001_restructure_user_addresses.sql
+BEGIN;
+
+-- Create new address table for normalized structure
+CREATE TABLE user_addresses (
+  id SERIAL PRIMARY KEY,
+  user_id INTEGER REFERENCES users(id),
+  street VARCHAR(255),
+  city VARCHAR(100),
+  state VARCHAR(2),
+  postal_code VARCHAR(10),
+  created_at TIMESTAMP DEFAULT NOW()
+);
+
+-- Migrate existing flat data to nested structure
+INSERT INTO user_addresses (user_id, street, city, state, postal_code)
+SELECT id, street, city, state, zip
+FROM users
+WHERE street IS NOT NULL;
+
+-- Add foreign key to users table
+ALTER TABLE users ADD COLUMN address_id INTEGER REFERENCES user_addresses(id);
+
+UPDATE users u
+SET address_id = ua.id
+FROM user_addresses ua
+WHERE u.id = ua.user_id;
+
+-- Deprecate old columns (don't drop yet for rollback safety)
+ALTER TABLE users
+  ALTER COLUMN street DROP NOT NULL,
+  ALTER COLUMN city DROP NOT NULL,
+  ALTER COLUMN state DROP NOT NULL,
+  ALTER COLUMN zip DROP NOT NULL;
+
+COMMIT;
+
+-- Rollback Script: 001_rollback_restructure.sql
+BEGIN;
+UPDATE users u
+SET street = ua.street,
+    city = ua.city,
+    state = ua.state,
+    zip = ua.postal_code
+FROM user_addresses ua
+WHERE u.address_id = ua.id;
+
+ALTER TABLE users DROP COLUMN address_id;
+DROP TABLE user_addresses;
+COMMIT;
+```
+
+### Example 2: GraphQL Schema Evolution
+
+```graphql
+# Schema v1 (Deprecated)
+type User {
+  id: ID!
+  username: String!  # DEPRECATED: Replaced by email
+  email: String
+  fullName: String
+}
+
+type Query {
+  user(id: ID!): User
+  users: [User!]!
+}
+
+# Schema v2 (Current)
+type Address {
+  street: String!
+  city: String!
+  state: String!
+  postalCode: String!
+  country: String!
+}
+
+type User {
+  id: ID!
+  email: String!  # Now required, primary identifier
+  username: String @deprecated(reason: "Use email instead. Removed in v3.")
+  profile: UserProfile!
+  address: Address
+}
+
+type UserProfile {
+  firstName: String!
+  lastName: String!
+  displayName: String!
+  avatar: String
+}
+
+type Query {
+  user(id: ID, email: String): User  # Multiple lookup options
+  users(filter: UserFilter): [User!]!
+}
+
+input UserFilter {
+  email: String
+  city: String
+  state: String
+}
+
+# Schema v3 (Planned)
+type User {
+  id: ID!
+  email: String!
+  profile: UserProfile!
+  addresses: [Address!]!  # Now supports multiple addresses
+}
+
+# Migration Resolver Implementation
+const resolvers = {
+  Query: {
+    user: async (_, args, context) => {
+      const version = context.apiVersion;
+
+      if (version === 'v1') {
+        // Legacy lookup by username
+        const user = await db.users.findByUsername(args.id);
+        return {
+          ...user,
+          username: user.username,  // Still supported in v1
+          fullName: `${user.firstName} ${user.lastName}`
+        };
+      } else {
+        // Modern lookup by email or ID
+        const user = await db.users.findOne({
+          where: args.email ? { email: args.email } : { id: args.id }
+        });
+        return user;
+      }
+    }
+  },
+
+  User: {
+    // Compatibility field resolver for deprecated username
+    username: (user, args, context) => {
+      if (context.apiVersion === 'v1') {
+        return user.username;
+      }
+      // Add deprecation warning to response headers
+      context.res.set('Deprecation', 'username field is deprecated. Use email.');
+      return user.username || user.email.split('@')[0];
+    },
+
+    // Transform flat structure to nested for v2+
+    profile: (user) => ({
+      firstName: user.firstName || user.fullName?.split(' ')[0],
+      lastName: user.lastName || user.fullName?.split(' ')[1],
+      displayName: user.fullName,
+      avatar: user.avatar
+    })
+  }
+};
+
+// Automated Schema Compatibility Tests
+describe('GraphQL Schema Migration Tests', () => {
+  test('v1 clients can still query with username', async () => {
+    const query = `query { user(id: "johndoe") { username email } }`;
+    const result = await executeQuery(query, { apiVersion: 'v1' });
+    expect(result.data.user.username).toBe('johndoe');
+  });
+
+  test('v2 clients receive nested profile structure', async () => {
+    const query = `query { user(email: "john@example.com") { profile { firstName lastName } } }`;
+    const result = await executeQuery(query, { apiVersion: 'v2' });
+    expect(result.data.user.profile.firstName).toBe('John');
+  });
+
+  test('deprecated fields trigger warning headers', async () => {
+    const query = `query { user(id: "123") { username } }`;
+    const { response } = await executeQueryWithHeaders(query, { apiVersion: 'v2' });
+    expect(response.headers.get('Deprecation')).toContain('username field is deprecated');
+  });
+});
+```
+
+### Example 3: gRPC Service Versioning
+
+```protobuf
+// service_v1.proto (Deprecated)
+syntax = "proto3";
+package user.v1;
+
+message User {
+  int32 id = 1;
+  string username = 2;
+  string email = 3;
+  string full_name = 4;
+}
+
+message GetUserRequest {
+  int32 id = 1;
+}
+
+message GetUserResponse {
+  User user = 1;
+}
+
+service UserService {
+  rpc GetUser(GetUserRequest) returns (GetUserResponse);
+}
+
+// service_v2.proto (Current)
+syntax = "proto3";
+package user.v2;
+
+import "google/protobuf/timestamp.proto";
+
+message Address {
+  string street = 1;
+  string city = 2;
+  string state = 3;
+  string postal_code = 4;
+  string country = 5;
+}
+
+message UserProfile {
+  string first_name = 1;
+  string last_name = 2;
+  string display_name = 3;
+  string avatar_url = 4;
+}
+
+message User {
+  int32 id = 1;
+  string email = 2;
+  UserProfile profile = 3;
+  Address address = 4;
+  google.protobuf.Timestamp created_at = 5;
+  google.protobuf.Timestamp updated_at = 6;
+}
+
+message GetUserRequest {
+  oneof identifier {
+    int32 id = 1;
+    string email = 2;
+  }
+}
+
+message GetUserResponse {
+  User user = 1;
+}
+
+service UserService {
+  rpc GetUser(GetUserRequest) returns (GetUserResponse);
+  rpc ListUsers(ListUsersRequest) returns (ListUsersResponse);
+}
+
+// Compatibility Bridge Service
+package user.bridge;
+
+import "user/v1/service.proto";
+import "user/v2/service.proto";
+
+class UserServiceBridge {
+  constructor() {
+    this.v2Service = new user.v2.UserServiceClient('localhost:50052');
+  }
+
+  // Implement v1 interface while calling v2 backend
+  async GetUser(call, callback) {
+    const v1Request = call.request;
+
+    // Transform v1 request to v2 format
+    const v2Request = {
+      id: v1Request.id
+    };
+
+    try {
+      const v2Response = await this.v2Service.GetUser(v2Request);
+      const v2User = v2Response.user;
+
+      // Transform v2 response back to v1 format
+      const v1User = {
+        id: v2User.id,
+        username: v2User.email.split('@')[0],  // Synthesize username
+        email: v2User.email,
+        full_name: v2User.profile.display_name
+      };
+
+      callback(null, { user: v1User });
+
+      // Log deprecation warning
+      console.warn(`[DEPRECATED] v1 API used by client ${call.getPeer()}`);
+
+    } catch (error) {
+      callback(error);
+    }
+  }
+}
+
+// Envoy gRPC Gateway Configuration for Version Routing
+static_resources:
+  listeners:
+    - name: user_service_listener
+      address:
+        socket_address:
+          address: 0.0.0.0
+          port_value: 50051
+      filter_chains:
+        - filters:
+            - name: envoy.filters.network.http_connection_manager
+              typed_config:
+                "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
+                stat_prefix: grpc_json
+                codec_type: AUTO
+                route_config:
+                  name: local_route
+                  virtual_hosts:
+                    - name: user_service
+                      domains: ["*"]
+                      routes:
+                        # Route v1 requests to compatibility bridge
+                        - match:
+                            prefix: "/user.v1.UserService"
+                          route:
+                            cluster: user_service_v1_bridge
+                            timeout: 30s
+                        # Route v2 requests to native service
+                        - match:
+                            prefix: "/user.v2.UserService"
+                          route:
+                            cluster: user_service_v2
+                            timeout: 30s
+
+  clusters:
+    - name: user_service_v1_bridge
+      connect_timeout: 1s
+      type: STRICT_DNS
+      lb_policy: ROUND_ROBIN
+      http2_protocol_options: {}
+      load_assignment:
+        cluster_name: user_service_v1_bridge
+        endpoints:
+          - lb_endpoints:
+              - endpoint:
+                  address:
+                    socket_address:
+                      address: user-bridge-service
+                      port_value: 50051
+
+    - name: user_service_v2
+      connect_timeout: 1s
+      type: STRICT_DNS
+      lb_policy: ROUND_ROBIN
+      http2_protocol_options: {}
+      load_assignment:
+        cluster_name: user_service_v2
+        endpoints:
+          - lb_endpoints:
+              - endpoint:
+                  address:
+                    socket_address:
+                      address: user-service-v2
+                      port_value: 50052
+
+// Migration Testing Framework
+describe('gRPC API Migration Tests', () => {
+  const v1Client = new user.v1.UserServiceClient('localhost:50051');
+  const v2Client = new user.v2.UserServiceClient('localhost:50052');
+
+  test('v1 clients receive compatible responses', async () => {
+    const request = new user.v1.GetUserRequest({ id: 123 });
+    const response = await v1Client.GetUser(request);
+
+    expect(response.user.username).toBeDefined();
+    expect(response.user.email).toBeDefined();
+    expect(response.user.full_name).toBeDefined();
+  });
+
+  test('v2 clients receive enhanced data structures', async () => {
+    const request = new user.v2.GetUserRequest({ email: 'john@example.com' });
+    const response = await v2Client.GetUser(request);
+
+    expect(response.user.profile).toBeDefined();
+    expect(response.user.profile.first_name).toBeDefined();
+    expect(response.user.address).toBeDefined();
+  });
+
+  test('data consistency between versions', async () => {
+    const userId = 123;
+
+    const v1Response = await v1Client.GetUser({ id: userId });
+    const v2Response = await v2Client.GetUser({ id: userId });
+
+    // Verify transformed data matches
+    expect(v1Response.user.email).toBe(v2Response.user.email);
+    expect(v1Response.user.full_name).toBe(v2Response.user.profile.display_name);
+  });
+});
+```
+
+## Configuration Options
+
+**Basic Usage:**
+```bash
+/migrate-api \
+  --source=v1 \
+  --target=v2 \
+  --api-spec=openapi.yaml \
+  --consumers=consumer-registry.json
+```
+
+**Available Options:**
+
+`--strategy <type>` - Migration deployment strategy
+- `canary` - Gradual traffic shifting (default, safest)
+- `blue-green` - Instant switchover with rollback capability
+- `rolling` - Progressive deployment across instances
+- `feature-flag` - Application-controlled version selection
+- `parallel-run` - Run both versions, compare results
+
+`--compatibility-mode <mode>` - Backward compatibility approach
+- `adapter` - Transform requests/responses between versions (default)
+- `proxy` - Route old endpoints to new implementation
+- `shim` - Minimal compatibility layer, consumers must adapt
+- `none` - No compatibility, hard cutover (dangerous)
+
+`--deprecation-period <duration>` - Support window for old version
+- `3months` - Short deprecation (minor changes)
+- `6months` - Standard deprecation (default)
+- `12months` - Extended support (major changes)
+- `custom:YYYY-MM-DD` - Specific sunset date
+
+`--breaking-changes-policy <policy>` - How to handle breaking changes
+- `require-adapters` - Force compatibility layer generation
+- `warn-consumers` - Send notifications, allow migration time
+- `block-deployment` - Prevent deploy until consumers updated
+- `document-only` - Just update documentation
+
+`--traffic-split <percentage>` - Initial new version traffic
+- Default: `0` (dark launch)
+- Range: 0-100
+- Example: `10` for 10% canary deployment
+
+`--rollback-threshold <percentage>` - Error rate trigger for auto-rollback
+- Default: `5` (5% error rate)
+- Range: 1-50
+- Example: `2` for strict quality requirements
+
+`--test-coverage-required <percentage>` - Minimum test coverage before deploy
+- Default: `80`
+- Range: 0-100
+- Blocks deployment if coverage below threshold
+
+`--generate-migration-guide` - Create consumer migration documentation
+- Generates markdown guide with code examples
+- Includes breaking change summaries
+- Provides timeline and support contacts
+
+`--dry-run` - Simulate migration without making changes
+- Analyze breaking changes
+- Generate compatibility report
+- Estimate migration effort
+- No actual deployment
+
+## Error Handling
+
+**Common Errors and Solutions:**
+
+**Error: Breaking changes detected without compatibility layer**
+```
+ERROR: 15 breaking changes detected in target API version
+- Removed field: User.username (affects 12 endpoints)
+- Changed type: Order.total (string → number)
+- Renamed endpoint: /users/search → /users/find
+
+Solution: Either:
+1. Add --compatibility-mode=adapter to generate transformers
+2. Create manual adapters in adapters/ directory
+3. Use --breaking-changes-policy=warn-consumers for grace period
+```
+
+**Error: Consumer test failures in compatibility mode**
+```
+ERROR: 3 consumer integration tests failed with v2 adapter
+- AcmeApp: Expected username field, received null
+- BetaCorp: Response schema validation failed
+- GammaInc: Authentication token format mismatch
+
+Solution:
+1. Review consumer test failures: npm run test:consumers
+2. Update adapters to handle edge cases
+3. Contact affected consumers for migration coordination
+4. Use --traffic-split=0 for dark launch until resolved
+```
+
+**Error: Database migration rollback required**
+```
+ERROR: Migration script 003_add_foreign_keys.sql failed
+Constraint violation: user_addresses.user_id references missing users
+
+Solution:
+1. Execute rollback: psql -f 003_rollback.sql
+2. Fix data inconsistencies: npm run data:cleanup
+3. Re-run migration with --validate-data flag
+4. Check migration logs: tail -f logs/migration.log
+```
+
+**Error: Traffic spike indicating rollback needed**
+```
+WARNING: v1 traffic increased from 10% to 45% in 5 minutes
+Possible rollback from consumers due to v2 issues
+
+Solution:
+1. Check v2 error rates: /metrics/api/v2/errors
+2. Review recent v2 deployment logs
+3. Pause traffic shift: kubectl patch deployment api-gateway --type=json -p='[{"op":"replace","path":"/spec/template/spec/containers/0/env/1/value","value":"10"}]'
+4. Investigate root cause before continuing rollout
+```
+
+**Error: Incompatible schema versions in distributed system**
+```
+ERROR: Service A running v2 schema, Service B still on v1
+Message deserialization failed: unknown field 'profile'
+
+Solution:
+1. Implement schema registry: npm install @kafkajs/schema-registry
+2. Use forward-compatible schemas with optional fields
+3. Deploy with version negotiation: --enable-version-negotiation
+4. Coordinate deployment order across services
+```
+
+## Best Practices
+
+**DO:**
+- Start with comprehensive API usage analysis before planning migration
+- Generate automated compatibility tests for all breaking changes
+- Implement feature flags for granular control over version activation
+- Use semantic versioning and clearly communicate breaking changes
+- Monitor error rates and latency separately for each API version
+- Maintain detailed migration documentation with timelines
+- Create rollback procedures and test them before deployment
+- Send deprecation warnings months before sunset dates
+- Provide sandbox environments for consumers to test migrations
+- Use API gateways for centralized version routing and monitoring
+
+**DON'T:**
+- Deploy breaking changes without backward compatibility period
+- Remove deprecated endpoints immediately after new version launch
+- Skip comprehensive testing of compatibility layers under load
+- Assume all consumers will migrate quickly (expect stragglers)
+- Make multiple major version jumps simultaneously
+- Ignore consumer feedback during migration planning
+- Deploy migrations during peak traffic periods
+- Use hard deadlines without grace period extensions
+- Forget to version your database schema along with API
+- Mix multiple unrelated breaking changes in single version
+
+**TIPS:**
+- Use OpenAPI diff tools to automatically detect breaking changes
+- Implement consumer registry to track who uses which endpoints
+- Add X-API-Version header to all responses for debugging
+- Create automated alerts for unexpected version usage patterns
+- Use GraphQL deprecation directives for gradual field removal
+- Maintain change logs with migration impact assessments
+- Build compatibility dashboards showing adoption rates
+- Provide SDK updates simultaneously with API versions
+- Consider GraphQL for more flexible schema evolution
+- Use contract testing to verify consumer compatibility
+
+## Related Commands
+
+- `/api-contract-generator` - Generate OpenAPI specs from code
+- `/api-versioning-manager` - Manage multiple API versions
+- `/api-documentation-generator` - Update docs for new versions
+- `/api-monitoring-dashboard` - Track version adoption metrics
+- `/api-security-scanner` - Audit security across versions
+- `/api-load-tester` - Performance test both versions
+- `/api-sdk-generator` - Create client libraries for v2
+
+## Performance Considerations
+
+**Migration Performance Impact:**
+- Compatibility adapters add 5-20ms latency per request
+- Dual-write patterns during migration can double database load
+- Traffic splitting requires load balancer state management
+- Monitoring overhead increases with multiple active versions
+
+**Optimization Strategies:**
+- Cache adapter transformation results for identical requests
+- Use asynchronous migration for non-critical data changes
+- Implement read-through caches for backward compatibility lookups
+- Batch database migrations during low-traffic windows
+- Pre-warm caches before traffic switch to new version
+- Use connection pooling to handle parallel version load
+- Consider edge caching for frequently accessed compatibility transformations
+
+**Capacity Planning:**
+- Expect 20-30% overhead during dual-version support period
+- Plan for 2x database capacity during migration window
+- Allocate extra API gateway resources for routing logic
+- Monitor memory usage in compatibility layer services
+- Scale horizontally rather than vertically for version isolation
+
+## Security Considerations
+
+**Version Transition Security:**
+- Audit authentication mechanisms for compatibility breaks
+- Verify authorization rules apply consistently across versions
+- Scan for security vulnerabilities in compatibility adapters
+- Review CORS policies for new version endpoints
+- Update API keys and tokens if authentication changes
+- Test rate limiting separately per API version
+- Ensure TLS/SSL certificates cover new version domains
+- Validate input sanitization in transformation layers
+- Check for data leakage in error messages across versions
+- Review audit logging captures version information
+
+**Security Checklist:**
+- [ ] Authentication backward compatible or migration path clear
+- [ ] Authorization policies tested with both version payloads
+- [ ] Sensitive data transformations don't expose information
+- [ ] Rate limiting prevents abuse of compatibility layers
+- [ ] API keys revocation works across all versions
+- [ ] Security headers consistent across versions
+- [ ] OWASP Top 10 validated for new endpoints
+- [ ] Penetration testing completed for v2 before public launch
+
+## Troubleshooting Guide
+
+**Issue: Consumers report intermittent failures after migration**
+- Check load balancer health checks for version endpoints
+- Verify DNS propagation completed for new version domains
+- Review session affinity settings (sticky sessions may cause issues)
+- Confirm database connection pools sized for dual version load
+- Check for race conditions in data migration scripts
+
+**Issue: Adapter performance degrading over time**
+- Monitor adapter service memory for leaks
+- Check for unbounded cache growth in transformation layer
+- Review database query performance for compatibility lookups
+- Consider pre-computing common transformations
+- Profile adapter code for inefficient object mapping
+
+**Issue: Version metrics not appearing in dashboard**
+- Verify X-API-Version header added to all responses
+- Check logging configuration captures version metadata
+- Confirm monitoring agents updated to track new version
+- Review metric aggregation rules in monitoring system
+- Ensure API gateway properly tags requests by version
+
+**Issue: Rollback triggered unexpectedly**
+- Review error rate thresholds (may be too sensitive)
+- Check if external service outages affected v2 only
+- Verify rollback threshold uses appropriate time windows
+- Investigate false positives in health checks
+- Review deployment timing vs. traffic pattern changes
+
+## Version History
+
+**v1.0.0** (2024-01-15)
+- Initial release with REST API migration support
+- Basic compatibility adapter generation
+- Canary deployment strategy
+- OpenAPI 3.0 diff analysis
+
+**v1.1.0** (2024-02-10)
+- Added GraphQL schema evolution support
+- Implemented automatic deprecation warning injection
+- Enhanced consumer notification system
+- Added rollback automation based on error thresholds
+
+**v1.2.0** (2024-03-05)
+- gRPC service versioning support with Envoy integration
+- Blue-green deployment strategy option
+- Database schema migration with automated rollback
+- Consumer registry integration for impact analysis
+
+**v1.3.0** (2024-04-20)
+- Feature flag integration for gradual rollout control
+- Enhanced compatibility testing framework
+- Performance optimization for adapter transformations
+- Multi-region migration coordination
+
+**v2.0.0** (2024-06-15)
+- Complete rewrite of adapter generation engine
+- Support for complex data transformation scenarios
+- Integration with major API gateway platforms
+- Real-time migration dashboard with adoption metrics
+- Automated consumer SDK generation for new versions
+
+**v2.1.0** (2024-08-30) - Current
+- AI-powered breaking change impact analysis
+- Automated migration guide generation
+- Enhanced security scanning for version transitions
+- Support for WebSocket and Server-Sent Events migration
+- Contract testing automation across API versions