Framework and Technology Migrations with AI

Technology migrations are among the most challenging tasks in software development. This lesson demonstrates how Cursor IDE’s AI capabilities transform complex migrations—from framework upgrades to complete platform changes—into manageable, systematic processes.

AI-Powered Migration Strategy

Traditional migrations require deep knowledge of both source and target technologies, often leading to months of careful planning and execution. AI assistance accelerates this process by automating code transformation, identifying patterns, and ensuring nothing is missed.

Migration Challenges AI Addresses

Code Transformation

AI automates syntax and pattern conversion between technologies

Dependency Mapping

AI identifies equivalent libraries and suggests replacements

Testing Coverage

AI ensures functionality is preserved through comprehensive testing

Incremental Migration

AI helps plan and execute gradual migration strategies

Frontend Framework Migrations

React to Next.js Migration

1. Project Analysis

   // Ask AI to analyze existing React project
   "Analyze this React application and create a migration plan to Next.js 14:
   - Identify routing patterns to convert to App Router
   - Find data fetching patterns to convert to Server Components
   - List state management that needs adjustment
   - Identify API calls to convert to Server Actions
   - Check for incompatible dependencies"

2. Migration Strategy

   // AI creates migration roadmap
   "Create a phased migration plan:
   Phase 1: Set up Next.js alongside React
   Phase 2: Migrate routing and layouts
   Phase 3: Convert components to Server Components
   Phase 4: Migrate state management
   Phase 5: Optimize and remove old code"
   
   // AI generates migration checklist
   interface MigrationPlan {
     phases: {
       name: string;
       tasks: MigrationTask[];
       estimatedDays: number;
       risks: string[];
     }[];
   
     rollbackStrategy: string;
     testingStrategy: string;
   }

3. Component Migration

   // AI converts React components to Next.js
   "Convert this React component to Next.js Server Component:
   - Move client-side logic to 'use client' components
   - Convert data fetching to async server component
   - Update imports for Next.js specific features
   - Optimize for server-side rendering"
   
   // Before: React Component
   import React, { useState, useEffect } from 'react';
   import { useParams } from 'react-router-dom';
   
   export function ProductPage() {
     const { id } = useParams();
     const [product, setProduct] = useState(null);
     const [loading, setLoading] = useState(true);
   
     useEffect(() => {
       fetch(`/api/products/${id}`)
         .then(res => res.json())
         .then(data => {
           setProduct(data);
           setLoading(false);
         });
     }, [id]);
   
     if (loading) return <div>Loading...</div>;
   
     return (
       <div>
         <h1>{product.name}</h1>
         <p>{product.description}</p>
         <AddToCartButton productId={product.id} />
       </div>
     );
   }
   
   // After: Next.js Server Component (AI generated)
   import { notFound } from 'next/navigation';
   import { AddToCartButton } from './AddToCartButton';
   
   async function getProduct(id: string) {
     const res = await fetch(`${process.env.API_URL}/products/${id}`, {
       next: { revalidate: 3600 } // Cache for 1 hour
     });
   
     if (!res.ok) return null;
     return res.json();
   }
   
   export default async function ProductPage({
     params
   }: {
     params: { id: string }
   }) {
     const product = await getProduct(params.id);
   
     if (!product) {
       notFound();
     }
   
     return (
       <div>
         <h1>{product.name}</h1>
         <p>{product.description}</p>
         <AddToCartButton productId={product.id} />
       </div>
     );
   }
   
   // Client Component (AddToCartButton.tsx)
   'use client';
   
   import { useState } from 'react';
   
   export function AddToCartButton({ productId }: { productId: string }) {
     const [isAdding, setIsAdding] = useState(false);
   
     const handleAddToCart = async () => {
       setIsAdding(true);
       // Add to cart logic
       setIsAdding(false);
     };
   
     return (
       <button
         onClick={handleAddToCart}
         disabled={isAdding}
       >
         {isAdding ? 'Adding...' : 'Add to Cart'}
       </button>
     );
   }

Vue to Nuxt Migration

Component Migration

<!-- AI converts Vue SFC to Nuxt -->
"Convert Vue 3 component to Nuxt 3:
- Update to Nuxt auto-imports
- Convert to composition API if needed
- Use Nuxt composables
- Handle async data with useAsyncData"

<!-- Before: Vue Component -->
<template>
  <div v-if="!loading">
    <h1>{{ user.name }}</h1>
    <UserPosts :user-id="user.id" />
  </div>
  <div v-else>Loading...</div>
</template>

<script>
import { ref, onMounted } from 'vue'
import axios from 'axios'
import UserPosts from './UserPosts.vue'

export default {
  components: { UserPosts },
  props: ['userId'],
  setup(props) {
    const user = ref(null)
    const loading = ref(true)

    onMounted(async () => {
      try {
        const { data } = await axios.get(`/api/users/${props.userId}`)
        user.value = data
      } finally {
        loading.value = false
      }
    })

    return { user, loading }
  }
}
</script>

<!-- After: Nuxt Component (AI generated) -->
<template>
  <div>
    <h1>{{ user.name }}</h1>
    <UserPosts :user-id="user.id" />
  </div>
</template>

<script setup lang="ts">
interface User {
  id: string
  name: string
}

const props = defineProps<{
  userId: string
}>()

const { data: user } = await useAsyncData<User>(
  `user-${props.userId}`,
  () => $fetch(`/api/users/${props.userId}`)
)

if (!user.value) {
  throw createError({
    statusCode: 404,
    statusMessage: 'User not found'
  })
}
</script>

Store Migration

// AI converts Vuex to Pinia
"Migrate Vuex store to Pinia for Nuxt 3:
- Convert modules to stores
- Update getters to computed
- Convert actions to methods
- Handle persistence"

// Before: Vuex Store
export const userModule = {
  namespaced: true,
  state: () => ({
    currentUser: null,
    users: [],
    loading: false
  }),
  getters: {
    isAuthenticated: state => !!state.currentUser,
    getUserById: state => id =>
      state.users.find(user => user.id === id)
  },
  mutations: {
    SET_CURRENT_USER(state, user) {
      state.currentUser = user
    },
    SET_USERS(state, users) {
      state.users = users
    },
    SET_LOADING(state, loading) {
      state.loading = loading
    }
  },
  actions: {
    async login({ commit }, credentials) {
      commit('SET_LOADING', true)
      try {
        const user = await authApi.login(credentials)
        commit('SET_CURRENT_USER', user)
        return user
      } finally {
        commit('SET_LOADING', false)
      }
    },
    async fetchUsers({ commit }) {
      const users = await userApi.getAll()
      commit('SET_USERS', users)
    }
  }
}

// After: Pinia Store (AI generated)
export const useUserStore = defineStore('user', () => {
  // State
  const currentUser = ref<User | null>(null)
  const users = ref<User[]>([])
  const loading = ref(false)

  // Getters
  const isAuthenticated = computed(() => !!currentUser.value)
  const getUserById = computed(() =>
    (id: string) => users.value.find(user => user.id === id)
  )

  // Actions
  async function login(credentials: LoginCredentials) {
    loading.value = true
    try {
      const user = await $fetch('/api/auth/login', {
        method: 'POST',
        body: credentials
      })
      currentUser.value = user

      // Refresh on client-side navigation
      await navigateTo('/dashboard')
      return user
    } finally {
      loading.value = false
    }
  }

  async function fetchUsers() {
    users.value = await $fetch('/api/users')
  }

  // Persist auth state
  const nuxtApp = useNuxtApp()
  if (process.client) {
    nuxtApp.hook('app:mounted', () => {
      const stored = localStorage.getItem('auth_token')
      if (stored) {
        // Restore session
      }
    })
  }

  return {
    // State
    currentUser: readonly(currentUser),
    users: readonly(users),
    loading: readonly(loading),

    // Getters
    isAuthenticated,
    getUserById,

    // Actions
    login,
    fetchUsers
  }
})

Backend Framework Migrations

Express to Fastify Migration

// AI assists with Express to Fastify migration
"Migrate Express app to Fastify:
- Convert middleware to Fastify plugins
- Update route handlers
- Migrate validation to Fastify schemas
- Convert error handling
- Update tests"

// Before: Express App
import express from 'express';
import bodyParser from 'body-parser';
import cors from 'cors';
import { authenticate } from './middleware/auth';
import { validate } from './middleware/validate';
import { userSchema } from './schemas/user';

const app = express();

app.use(cors());
app.use(bodyParser.json());

app.post('/users',
  authenticate,
  validate(userSchema),
  async (req, res, next) => {
    try {
      const user = await createUser(req.body);
      res.status(201).json(user);
    } catch (error) {
      next(error);
    }
  }
);

app.use((err, req, res, next) => {
  res.status(err.status || 500).json({
    error: err.message
  });
});

// After: Fastify App (AI generated)
import Fastify from 'fastify';
import cors from '@fastify/cors';
import { Type } from '@sinclair/typebox';

const fastify = Fastify({
  logger: true,
  ajv: {
    customOptions: {
      removeAdditional: 'all',
      coerceTypes: true
    }
  }
});

// Register plugins
await fastify.register(cors);
await fastify.register(authenticate);

// Schema definition
const createUserSchema = {
  body: Type.Object({
    email: Type.String({ format: 'email' }),
    password: Type.String({ minLength: 8 }),
    name: Type.String()
  }),
  response: {
    201: Type.Object({
      id: Type.String(),
      email: Type.String(),
      name: Type.String(),
      createdAt: Type.String({ format: 'date-time' })
    })
  }
};

// Route handler
fastify.post('/users', {
  schema: createUserSchema,
  preHandler: fastify.auth([fastify.verifyJWT])
}, async (request, reply) => {
  const user = await createUser(request.body);
  return reply.code(201).send(user);
});

// Error handling
fastify.setErrorHandler((error, request, reply) => {
  request.log.error(error);

  const statusCode = error.statusCode || 500;
  const response = {
    error: error.message,
    statusCode
  };

  reply.status(statusCode).send(response);
});

// Authentication plugin
async function authenticate(fastify, options) {
  fastify.decorate('verifyJWT', async (request, reply) => {
    try {
      const token = request.headers.authorization?.replace('Bearer ', '');
      if (!token) throw new Error('Missing token');

      const decoded = fastify.jwt.verify(token);
      request.user = decoded;
    } catch (err) {
      reply.code(401).send({ error: 'Unauthorized' });
    }
  });
}

Database Migration Strategies

AI Migration Planning

Ask AI to analyze your database and create a migration plan:

• “Analyze MongoDB schema and plan PostgreSQL migration”
• “Convert MySQL queries to PostgreSQL syntax”
• “Design data transformation pipeline”
• “Create rollback procedures”

// AI creates database migration pipeline
"Create database migration from MongoDB to PostgreSQL:
- Schema mapping and normalization
- Data transformation scripts
- Incremental sync during transition
- Validation and reconciliation
- Rollback capability"

export class DatabaseMigrator {
  private source: MongoClient;
  private target: PostgresClient;
  private validator: DataValidator;

  async analyzeSchemaDifferences() {
    // AI analyzes MongoDB collections
    const collections = await this.source.listCollections();
    const schemaMappings: SchemaMapping[] = [];

    for (const collection of collections) {
      const sample = await this.source
        .collection(collection)
        .find()
        .limit(1000)
        .toArray();

      // Infer schema from documents
      const mongoSchema = this.inferSchema(sample);

      // Generate PostgreSQL schema
      const pgSchema = this.generatePostgresSchema(
        collection,
        mongoSchema
      );

      schemaMappings.push({
        source: collection,
        target: pgSchema,
        transformations: this.identifyTransformations(mongoSchema, pgSchema)
      });
    }

    return schemaMappings;
  }

  async migrateCollection(mapping: SchemaMapping) {
    const batchSize = 1000;
    let offset = 0;
    let hasMore = true;

    // Create target table
    await this.createPostgresTable(mapping.target);

    while (hasMore) {
      // Fetch batch from MongoDB
      const documents = await this.source
        .collection(mapping.source)
        .find()
        .skip(offset)
        .limit(batchSize)
        .toArray();

      if (documents.length === 0) {
        hasMore = false;
        continue;
      }

      // Transform documents
      const rows = await this.transformDocuments(
        documents,
        mapping.transformations
      );

      // Insert into PostgreSQL
      await this.batchInsert(mapping.target.table, rows);

      // Validate migrated data
      await this.validator.validateBatch(
        mapping.source,
        mapping.target.table,
        offset,
        batchSize
      );

      offset += batchSize;

      // Log progress
      this.logger.info(`Migrated ${offset} documents from ${mapping.source}`);
    }
  }

  private generatePostgresSchema(
    collectionName: string,
    mongoSchema: any
  ): PostgresSchema {
    // AI generates normalized schema
    const tables: TableDefinition[] = [];

    // Main table
    const mainTable: TableDefinition = {
      name: collectionName,
      columns: []
    };

    // Analyze fields
    for (const [field, info] of Object.entries(mongoSchema)) {
      if (info.type === 'array' && info.itemType === 'object') {
        // Create separate table for array of objects
        tables.push(this.createChildTable(collectionName, field, info));

        // Add foreign key reference
        mainTable.columns.push({
          name: `${field}_id`,
          type: 'UUID',
          references: `${collectionName}_${field}.id`
        });
      } else if (info.type === 'object') {
        // Flatten nested objects
        const flattened = this.flattenObject(field, info);
        mainTable.columns.push(...flattened);
      } else {
        // Direct mapping
        mainTable.columns.push({
          name: field,
          type: this.mapMongoTypeToPostgres(info.type),
          nullable: info.nullable
        });
      }
    }

    tables.unshift(mainTable);

    return {
      tables,
      indexes: this.generateIndexes(mongoSchema),
      constraints: this.generateConstraints(mongoSchema)
    };
  }
}

Language Migration

JavaScript to TypeScript

// AI converts JavaScript to TypeScript
"Convert JavaScript codebase to TypeScript:
- Add type definitions
- Convert to strict mode
- Generate interfaces from usage
- Handle any types progressively
- Update build configuration"

// AI migration strategy
class TypeScriptMigrator {
  async migrateFile(filePath: string) {
    const content = await fs.readFile(filePath, 'utf-8');

    // Parse JavaScript AST
    const ast = parse(content);

    // Infer types from usage
    const typeInfo = await this.inferTypes(ast);

    // Generate TypeScript
    const tsContent = this.generateTypeScript(ast, typeInfo);

    // Add type imports
    const withImports = this.addTypeImports(tsContent, typeInfo);

    // Write TypeScript file
    const tsPath = filePath.replace('.js', '.ts');
    await fs.writeFile(tsPath, withImports);

    // Validate compilation
    await this.validateTypeScript(tsPath);
  }

  private inferTypes(ast: AST): TypeInfo {
    // AI analyzes code patterns
    const functions = this.extractFunctions(ast);
    const typeInfo: TypeInfo = {};

    for (const func of functions) {
      // Analyze parameter usage
      const params = func.params.map(param => {
        const usage = this.findParameterUsage(param, func.body);
        return {
          name: param.name,
          type: this.inferTypeFromUsage(usage)
        };
      });

      // Analyze return type
      const returnType = this.inferReturnType(func);

      typeInfo[func.name] = {
        params,
        returnType
      };
    }

    return typeInfo;
  }
}

// Example conversion
// Before: JavaScript
function processUser(user, options) {
  if (!user.id) {
    throw new Error('User ID required');
  }

  const result = {
    id: user.id,
    name: user.name || 'Unknown',
    email: user.email,
    isActive: options?.active !== false,
    metadata: {}
  };

  if (options?.includeMetadata) {
    result.metadata = {
      createdAt: user.createdAt,
      lastLogin: user.lastLogin
    };
  }

  return result;
}

// After: TypeScript (AI generated)
interface User {
  id: string;
  name?: string;
  email: string;
  createdAt?: Date;
  lastLogin?: Date;
}

interface ProcessUserOptions {
  active?: boolean;
  includeMetadata?: boolean;
}

interface ProcessedUser {
  id: string;
  name: string;
  email: string;
  isActive: boolean;
  metadata: {
    createdAt?: Date;
    lastLogin?: Date;
  };
}

function processUser(
  user: User,
  options?: ProcessUserOptions
): ProcessedUser {
  if (!user.id) {
    throw new Error('User ID required');
  }

  const result: ProcessedUser = {
    id: user.id,
    name: user.name || 'Unknown',
    email: user.email,
    isActive: options?.active !== false,
    metadata: {}
  };

  if (options?.includeMetadata) {
    result.metadata = {
      createdAt: user.createdAt,
      lastLogin: user.lastLogin
    };
  }

  return result;
}

Platform Migrations

Monolith to Microservices

Service Extraction

Identify and extract bounded contexts

API Gateway

Create unified API interface

Data Separation

Split shared databases safely

Gradual Migration

Strangler fig pattern implementation

// AI helps decompose monolith
"Analyze monolith and suggest microservices architecture:
- Identify bounded contexts
- Map dependencies
- Suggest service boundaries
- Plan database separation
- Create migration roadmap"

export class MicroservicesExtractor {
  async analyzeMonolith(codebasePath: string) {
    // Analyze code structure
    const modules = await this.identifyModules(codebasePath);
    const dependencies = await this.analyzeDependencies(modules);

    // Identify service candidates
    const services = this.identifyBoundedContexts(modules, dependencies);

    // Generate service definitions
    return services.map(service => ({
      name: service.name,
      responsibilities: service.modules,
      dependencies: this.getServiceDependencies(service, services),
      api: this.generateServiceAPI(service),
      database: this.planDatabaseSeparation(service),
      migrationPhase: this.calculateMigrationPhase(service, dependencies)
    }));
  }

  async extractService(
    serviceDef: ServiceDefinition,
    monolithPath: string
  ) {
    // Create service structure
    const servicePath = `./services/${serviceDef.name}`;
    await this.createServiceScaffold(servicePath);

    // Extract code modules
    for (const module of serviceDef.responsibilities) {
      await this.extractModule(
        `${monolithPath}/${module}`,
        `${servicePath}/src/${module}`
      );
    }

    // Generate service API
    await this.generateAPI(servicePath, serviceDef.api);

    // Create API client for monolith
    await this.generateClient(
      monolithPath,
      serviceDef.name,
      serviceDef.api
    );

    // Implement strangler pattern
    await this.implementStranglerProxy(
      monolithPath,
      serviceDef
    );
  }

  private async implementStranglerProxy(
    monolithPath: string,
    service: ServiceDefinition
  ) {
    // AI generates proxy code
    const proxyCode = `
    export class ${service.name}Proxy {
      private useNewService = process.env.USE_${service.name.toUpperCase()}_SERVICE === 'true';
      private client = new ${service.name}Client();
      private legacy = new Legacy${service.name}();

      async ${service.api.methods.map(method => `
        ${method.name}(${method.params}) {
          if (this.useNewService) {
            // Call new microservice
            return this.client.${method.name}(${method.params});
          } else {
            // Call legacy code
            return this.legacy.${method.name}(${method.params});
          }
        }
      `).join('\n')}

      // Gradual migration helper
      async migrateTraffic(percentage: number) {
        this.useNewService = Math.random() * 100 < percentage;
      }
    }`;

    await fs.writeFile(
      `${monolithPath}/proxies/${service.name}Proxy.ts`,
      proxyCode
    );
  }
}

Testing During Migration

Parallel Testing Strategy

// AI creates comprehensive testing strategy
"Create parallel testing for migration:
- Run tests against both old and new systems
- Compare results automatically
- Track parity metrics
- Identify discrepancies
- Performance comparison"

export class MigrationTester {
  async runParityTests(
    oldSystem: System,
    newSystem: System,
    testSuite: TestSuite
  ) {
    const results = {
      total: 0,
      passed: 0,
      failed: 0,
      discrepancies: []
    };

    for (const test of testSuite.tests) {
      results.total++;

      // Run against both systems
      const [oldResult, newResult] = await Promise.all([
        this.runTest(oldSystem, test),
        this.runTest(newSystem, test)
      ]);

      // Compare results
      const comparison = this.compareResults(oldResult, newResult);

      if (comparison.identical) {
        results.passed++;
      } else {
        results.failed++;
        results.discrepancies.push({
          test: test.name,
          differences: comparison.differences,
          oldResult: oldResult,
          newResult: newResult
        });
      }

      // Log progress
      this.logger.info(`Test ${test.name}: ${comparison.identical ? 'PASS' : 'FAIL'}`);
    }

    // Generate report
    await this.generateParityReport(results);

    return results;
  }

  async performanceComparison(
    oldSystem: System,
    newSystem: System
  ) {
    const metrics = {
      responseTime: {},
      throughput: {},
      resourceUsage: {}
    };

    // Load test scenarios
    const scenarios = await this.loadScenarios();

    for (const scenario of scenarios) {
      // Run performance test on old system
      const oldMetrics = await this.runLoadTest(oldSystem, scenario);

      // Run performance test on new system
      const newMetrics = await this.runLoadTest(newSystem, scenario);

      // Compare metrics
      metrics.responseTime[scenario.name] = {
        old: oldMetrics.avgResponseTime,
        new: newMetrics.avgResponseTime,
        improvement: ((oldMetrics.avgResponseTime - newMetrics.avgResponseTime) / oldMetrics.avgResponseTime) * 100
      };

      metrics.throughput[scenario.name] = {
        old: oldMetrics.requestsPerSecond,
        new: newMetrics.requestsPerSecond,
        improvement: ((newMetrics.requestsPerSecond - oldMetrics.requestsPerSecond) / oldMetrics.requestsPerSecond) * 100
      };
    }

    return metrics;
  }
}

Rollback and Recovery

Always Plan for Rollback

Every migration needs a rollback strategy:

• Database rollback scripts
• Feature flags for quick disable
• Traffic routing for gradual rollback
• Data reconciliation procedures

// AI implements rollback mechanisms
"Create rollback strategy for migration:
- Database rollback scripts
- Application version switching
- Data consistency checks
- Traffic management
- Communication plan"

export class RollbackManager {
  async prepareRollback(migration: Migration) {
    // Generate rollback scripts
    const rollbackPlan = {
      database: await this.generateDatabaseRollback(migration),
      application: await this.generateAppRollback(migration),
      configuration: await this.generateConfigRollback(migration),
      validation: await this.generateValidation(migration)
    };

    // Test rollback in staging
    await this.testRollback(rollbackPlan);

    return rollbackPlan;
  }

  async executeRollback(plan: RollbackPlan, reason: string) {
    this.logger.error(`Executing rollback: ${reason}`);

    // Stop new traffic
    await this.enableMaintenanceMode();

    try {
      // Rollback application
      await this.rollbackApplication(plan.application);

      // Rollback database if needed
      if (plan.database.hasSchemaChanges) {
        await this.rollbackDatabase(plan.database);
      }

      // Restore configuration
      await this.rollbackConfiguration(plan.configuration);

      // Validate system state
      const validation = await this.validateSystem(plan.validation);

      if (!validation.success) {
        throw new Error('Rollback validation failed');
      }

      // Resume traffic
      await this.disableMaintenanceMode();

      // Notify stakeholders
      await this.notifyRollback(reason, validation);

    } catch (error) {
      // Emergency procedures
      await this.executeEmergencyProcedures(error);
      throw error;
    }
  }
}

Practical Exercises

Exercise 1: Framework Migration

1. Choose a small React app to migrate to Next.js
2. Use AI to analyze the codebase
3. Create migration plan with phases
4. Execute migration incrementally
5. Validate functionality at each phase

Exercise 2: Database Migration

1. Design schema migration from NoSQL to SQL
2. Create data transformation scripts
3. Implement incremental sync
4. Validate data integrity
5. Switch over with zero downtime

Exercise 3: Microservices Extraction

1. Identify service boundary in monolith
2. Extract service with AI assistance
3. Implement strangler pattern
4. Create integration tests
5. Gradually shift traffic

Best Practices

Incremental Approach

Migrate in small, testable increments

Parallel Running

Run old and new systems in parallel during transition

Comprehensive Testing

Test functionality, performance, and edge cases

Rollback Ready

Always have a tested rollback plan

Next Steps

Architecture Design

Design target architecture before migration

Performance Optimization

Optimize during migration process

Team Training

Ensure team is ready for new technology

Migration Mastery

AI transforms complex migrations from risky endeavors into systematic, manageable processes. By leveraging AI for code analysis, transformation, and testing, you can execute migrations that would traditionally take months in a fraction of the time. Start with small components, validate thoroughly, and scale up confidence with each successful migration.