How to Handle Data in Microservices: Best Practices and Fixes

In microservices, each service should own its database to ensure data isolation and independence. Use event-driven communication or API calls for data sharing between services to maintain consistency and avoid tight coupling.

Why This Happens

Developers often try to share a single database across multiple microservices to simplify data access. This causes tight coupling, data conflicts, and scaling problems because services depend on the same data source.

Sharing databases breaks the microservices principle of independent deployability and ownership.

javascript

class UserService {
  constructor(db) {
    this.db = db; // Shared database instance
  }

  getUser(id) {
    return this.db.query(`SELECT * FROM users WHERE id = ${id}`);
  }
}

class OrderService {
  constructor(db) {
    this.db = db; // Same shared database
  }

  getOrders(userId) {
    return this.db.query(`SELECT * FROM orders WHERE user_id = ${userId}`);
  }
}

Output

Services become tightly coupled and any schema change affects all services, causing deployment and data consistency issues.

The Fix

Give each microservice its own database to own its data independently. Use APIs or events to communicate data changes between services. This keeps services decoupled and scalable.

For example, UserService and OrderService have separate databases and communicate via events or REST calls.

javascript

class UserService {
  constructor(userDb) {
    this.userDb = userDb; // Own database
  }

  getUser(id) {
    return this.userDb.query(`SELECT * FROM users WHERE id = ${id}`);
  }

  notifyUserCreated(user) {
    // Publish event to message broker
    eventBus.publish('UserCreated', user);
  }
}

class OrderService {
  constructor(orderDb) {
    this.orderDb = orderDb; // Own database
    eventBus.subscribe('UserCreated', (user) => {
      // Sync or react to user data
      this.createUserReference(user);
    });
  }

  getOrders(userId) {
    return this.orderDb.query(`SELECT * FROM orders WHERE user_id = ${userId}`);
  }
}

Output

Services operate independently with their own data stores and communicate asynchronously, improving scalability and reducing coupling.

Prevention

Always design microservices with database per service pattern to avoid shared data problems. Use event-driven architecture or API gateways for communication.

• Implement event sourcing or change data capture to sync data asynchronously.
• Use domain-driven design to define clear service boundaries.
• Automate schema changes and testing to prevent breaking changes.

Related Errors

Common related errors include:

• Data inconsistency: caused by direct database sharing or lack of synchronization.
• Tight coupling: services fail to deploy independently due to shared schemas.
• Performance bottlenecks: when one service's database load affects others.

Fixes involve separating databases, using asynchronous messaging, and applying circuit breakers for resilience.

Key Takeaways

Each microservice must own its database to ensure independence and scalability.

Use event-driven communication or APIs to share data between services safely.

Avoid direct database sharing to prevent tight coupling and data conflicts.

Design clear service boundaries using domain-driven design principles.

Automate testing and schema migrations to maintain data integrity.