01/12/26

How to Build Microservices with TypeScript

A practical guide to building distributed systems that don't fall apart

Ivan Cernja
12 Min Read

Microservices promise independent deployment, team autonomy, and better scalability. They also introduce network calls, distributed transactions, and operational complexity. This guide shows you how to build microservices in TypeScript while avoiding common pitfalls.

When to Use Microservices

Before diving in, be honest about whether you need microservices:

Start with a monolith if:

  • You're a small team (< 5 developers)
  • You're still figuring out domain boundaries
  • You want to ship quickly without infrastructure overhead

Consider microservices if:

  • Different parts of your system have different scaling needs
  • Teams need to deploy independently
  • You want fault isolation between components
  • Your domain has clear bounded contexts

The good news: with the right framework, you can start simple and split services later without rewriting everything.

Project Setup

We'll use Encore.ts because it handles the infrastructure complexity of microservices automatically. Service discovery, networking, databases per service, and distributed tracing all work out of the box. The patterns apply to other approaches, but you'd need to configure these yourself.

# Install Encore CLI
brew install encoredev/tap/encore

# Create a new app
encore app create shop-app --example=ts/empty
cd shop-app

# Start development
encore run

Your local development dashboard at localhost:9400 shows all services, their APIs, and how they connect. This becomes invaluable as your system grows.

Defining Services

In Encore, a service is a directory with an encore.service.ts file. Each service can have its own endpoints, database, and business logic. Let's build an e-commerce backend with three services:

/shop-app
├── encore.app
├── users/
│   ├── encore.service.ts
│   ├── users.ts
│   └── db.ts
├── products/
│   ├── encore.service.ts
│   ├── products.ts
│   └── db.ts
└── orders/
    ├── encore.service.ts
    ├── orders.ts
    └── db.ts

Each service owns its domain and database. This isolation means teams can work independently, and a bug in one service can't corrupt another's data.

Users Service

Create the service directory and declaration file. The service name appears in logs, traces, and the service catalog.

mkdir users

Create users/encore.service.ts:

import { Service } from "encore.dev/service";

export default new Service("users");

Create users/db.ts. Each service gets its own database, provisioned automatically. This is the "database per service" pattern that gives you isolation and independent scaling.

import { SQLDatabase } from "encore.dev/storage/sqldb";

export const db = new SQLDatabase("users", {
  migrations: "./migrations",
});

Create users/migrations/001_create_users.up.sql. Migrations run automatically when you start the app or deploy. Encore tracks which migrations have been applied.

CREATE TABLE users (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  email TEXT UNIQUE NOT NULL,
  name TEXT NOT NULL,
  created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
);

Create users/users.ts with the service's API endpoints:

import { api, APIError } from "encore.dev/api";
import { db } from "./db";

export interface User {
  id: string;
  email: string;
  name: string;
}

interface CreateUserRequest {
  email: string;
  name: string;
}

export const create = api(
  { expose: true, method: "POST", path: "/users" },
  async (req: CreateUserRequest): Promise<User> => {
    const row = await db.queryRow<User>`
      INSERT INTO users (email, name)
      VALUES (${req.email}, ${req.name})
      RETURNING id, email, name
    `;
    return row!;
  }
);

export const get = api(
  { expose: true, method: "GET", path: "/users/:id" },
  async ({ id }: { id: string }): Promise<User> => {
    const row = await db.queryRow<User>`
      SELECT id, email, name FROM users WHERE id = ${id}
    `;
    if (!row) {
      throw APIError.notFound("user not found");
    }
    return row;
  }
);

Products Service

Follow the same pattern for products. Each service is self-contained with its own database and endpoints.

Create products/encore.service.ts:

import { Service } from "encore.dev/service";

export default new Service("products");

Create products/db.ts:

import { SQLDatabase } from "encore.dev/storage/sqldb";

export const db = new SQLDatabase("products", {
  migrations: "./migrations",
});

Create products/migrations/001_create_products.up.sql:

CREATE TABLE products (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  name TEXT NOT NULL,
  price_cents INTEGER NOT NULL,
  inventory INTEGER NOT NULL DEFAULT 0
);

Create products/products.ts. Notice the reserveInventory endpoint doesn't have expose: true, making it an internal API only callable by other services, not external clients.

import { api, APIError } from "encore.dev/api";
import { db } from "./db";

export interface Product {
  id: string;
  name: string;
  priceCents: number;
  inventory: number;
}

interface CreateProductRequest {
  name: string;
  priceCents: number;
  inventory: number;
}

export const create = api(
  { expose: true, method: "POST", path: "/products" },
  async (req: CreateProductRequest): Promise<Product> => {
    const row = await db.queryRow<Product>`
      INSERT INTO products (name, price_cents, inventory)
      VALUES (${req.name}, ${req.priceCents}, ${req.inventory})
      RETURNING id, name, price_cents as "priceCents", inventory
    `;
    return row!;
  }
);

export const get = api(
  { expose: true, method: "GET", path: "/products/:id" },
  async ({ id }: { id: string }): Promise<Product> => {
    const row = await db.queryRow<Product>`
      SELECT id, name, price_cents as "priceCents", inventory 
      FROM products WHERE id = ${id}
    `;
    if (!row) {
      throw APIError.notFound("product not found");
    }
    return row;
  }
);

// Internal API for order service to reserve inventory
export const reserveInventory = api(
  { method: "POST", path: "/products/:id/reserve" },
  async ({ id, quantity }: { id: string; quantity: number }): Promise<void> => {
    const result = await db.exec`
      UPDATE products 
      SET inventory = inventory - ${quantity}
      WHERE id = ${id} AND inventory >= ${quantity}
    `;
    if (result.rowsAffected === 0) {
      throw APIError.failedPrecondition("insufficient inventory");
    }
  }
);

Orders Service

This is where services start talking to each other. The orders service needs to verify users exist and reserve product inventory before creating an order.

Create orders/encore.service.ts:

import { Service } from "encore.dev/service";

export default new Service("orders");

Create orders/db.ts:

import { SQLDatabase } from "encore.dev/storage/sqldb";

export const db = new SQLDatabase("orders", {
  migrations: "./migrations",
});

Create orders/migrations/001_create_orders.up.sql:

CREATE TABLE orders (
  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
  user_id UUID NOT NULL,
  product_id UUID NOT NULL,
  quantity INTEGER NOT NULL,
  total_cents INTEGER NOT NULL,
  status TEXT NOT NULL DEFAULT 'pending',
  created_at TIMESTAMP WITH TIME ZONE DEFAULT NOW()
);

Create orders/orders.ts. The magic happens in the imports: ~encore/clients gives you type-safe clients for calling other services. No HTTP boilerplate, no manual serialization, full IDE support.

import { api, APIError } from "encore.dev/api";
import { db } from "./db";
import { users } from "~encore/clients";
import { products } from "~encore/clients";

interface Order {
  id: string;
  userId: string;
  productId: string;
  quantity: number;
  totalCents: number;
  status: string;
}

interface CreateOrderRequest {
  userId: string;
  productId: string;
  quantity: number;
}

export const create = api(
  { expose: true, method: "POST", path: "/orders" },
  async (req: CreateOrderRequest): Promise<Order> => {
    // Verify user exists (throws if not found)
    await users.get({ id: req.userId });
    
    // Get product and verify it exists
    const product = await products.get({ id: req.productId });
    
    // Reserve inventory (throws if insufficient)
    await products.reserveInventory({
      id: req.productId,
      quantity: req.quantity,
    });
    
    // Calculate total
    const totalCents = product.priceCents * req.quantity;
    
    // Create order
    const row = await db.queryRow<Order>`
      INSERT INTO orders (user_id, product_id, quantity, total_cents, status)
      VALUES (${req.userId}, ${req.productId}, ${req.quantity}, ${totalCents}, 'confirmed')
      RETURNING id, user_id as "userId", product_id as "productId", 
                quantity, total_cents as "totalCents", status
    `;
    
    return row!;
  }
);

export const get = api(
  { expose: true, method: "GET", path: "/orders/:id" },
  async ({ id }: { id: string }): Promise<Order> => {
    const row = await db.queryRow<Order>`
      SELECT id, user_id as "userId", product_id as "productId",
             quantity, total_cents as "totalCents", status
      FROM orders WHERE id = ${id}
    `;
    if (!row) {
      throw APIError.notFound("order not found");
    }
    return row;
  }
);

Notice how clean service-to-service calls are:

import { users } from "~encore/clients";
import { products } from "~encore/clients";

// Call another service like a function
const user = await users.get({ id: req.userId });
const product = await products.get({ id: req.productId });

Encore generates type-safe clients automatically from your service definitions. You get compile-time checking that you're calling APIs correctly.

Adding Pub/Sub for Async Communication

Synchronous calls work for simple cases, but some operations should be async. You don't want order creation to block while sending a confirmation email. Let's add Pub/Sub for event-driven communication.

Create orders/events.ts. Topics are declared at the module level and can be published to from any service. The type parameter ensures all publishers send correctly shaped events.

import { Topic } from "encore.dev/pubsub";

export interface OrderCreatedEvent {
  orderId: string;
  userId: string;
  totalCents: number;
}

export const orderCreated = new Topic<OrderCreatedEvent>("order-created", {
  deliveryGuarantee: "at-least-once",
});

Update orders/orders.ts to publish the event after creating an order. Publishing is async and doesn't block the response to the client.

import { orderCreated } from "./events";

export const create = api(
  { expose: true, method: "POST", path: "/orders" },
  async (req: CreateOrderRequest): Promise<Order> => {
    // ... existing order creation logic ...
    
    // Publish event for async processing
    await orderCreated.publish({
      orderId: row!.id,
      userId: req.userId,
      totalCents,
    });
    
    return row!;
  }
);

Create a notifications service to handle emails. Subscriptions process events asynchronously, with automatic retries on failure.

Create notifications/encore.service.ts:

import { Service } from "encore.dev/service";

export default new Service("notifications");

Create notifications/notifications.ts. The subscription handler receives events and processes them independently of the original request.

import { Subscription } from "encore.dev/pubsub";
import { orderCreated } from "../orders/events";
import { users } from "~encore/clients";

// Subscribe to order events
const _ = new Subscription(orderCreated, "send-order-confirmation", {
  handler: async (event) => {
    // Get user details for the email
    const user = await users.get({ id: event.userId });
    
    // Send confirmation email
    await sendEmail({
      to: user.email,
      subject: "Order Confirmed",
      body: `Your order #${event.orderId} for $${(event.totalCents / 100).toFixed(2)} has been confirmed.`,
    });
    
    console.log(`Sent confirmation email to ${user.email}`);
  },
});

async function sendEmail(params: { to: string; subject: string; body: string }) {
  // Integrate with SendGrid, Resend, etc.
  console.log(`Email to ${params.to}: ${params.subject}`);
}

Now order creation is fast (synchronous database calls), and email sending happens in the background. If email sending fails, Pub/Sub retries automatically.

Service Architecture Visualization

After building these services, your architecture looks like this:

┌─────────┐     ┌──────────┐     ┌─────────────────┐
│  Users  │◄────│  Orders  │────►│    Products     │
│ Service │     │ Service  │     │    Service      │
└────┬────┘     └────┬─────┘     └────────┬────────┘
     │               │                    │
     ▼               ▼                    ▼
┌─────────┐     ┌──────────┐     ┌─────────────────┐
│ Users   │     │  Orders  │     │    Products     │
│   DB    │     │    DB    │     │       DB        │
└─────────┘     └──────────┘     └─────────────────┘
                     │
                     ▼ (Pub/Sub)
              ┌──────────────┐
              │ Notifications│
              │   Service    │
              └──────────────┘

Encore generates this diagram automatically from your code. Check the local dashboard at localhost:9400 to see it, or view architecture diagrams in Encore Cloud after deploying.

Encore architecture diagram

Distributed Tracing

With multiple services, debugging requires tracing requests across service boundaries. Encore handles this automatically with zero configuration.

Every request gets a trace ID that follows it through all service calls. In the dashboard, click any request to see:

  • Which services were called
  • How long each call took
  • Database queries in each service
  • Pub/Sub message publishing
  • Any errors that occurred

Encore distributed trace

No manual instrumentation needed. Learn more about distributed tracing.

Error Handling Across Services

When service B calls service A and A fails, B gets an error. Handle it appropriately by catching specific error types and returning meaningful errors to your callers.

import { APIError } from "encore.dev/api";
import { users } from "~encore/clients";

export const create = api(
  { expose: true, method: "POST", path: "/orders" },
  async (req: CreateOrderRequest): Promise<Order> => {
    try {
      await users.get({ id: req.userId });
    } catch (error) {
      if (error instanceof APIError && error.code === "not_found") {
        // Convert to a more meaningful error for our callers
        throw APIError.invalidArgument("user does not exist");
      }
      throw error; // Re-throw unexpected errors
    }
    
    // ... rest of handler
  }
);

Testing Microservices

Test services in isolation by calling their endpoints directly. Encore runs the full infrastructure during tests, so database operations work just like production.

import { describe, expect, test } from "vitest";
import { create, get } from "./users";

describe("users service", () => {
  test("create and get user", async () => {
    const user = await create({
      email: "[email protected]",
      name: "Test User",
    });
    
    expect(user.email).toBe("[email protected]");
    
    const fetched = await get({ id: user.id });
    expect(fetched.id).toBe(user.id);
  });
});

For integration tests that span services, Encore runs all services together. You can test the full order flow including service-to-service calls.

import { describe, expect, test } from "vitest";
import { create as createUser } from "../users/users";
import { create as createProduct } from "../products/products";
import { create as createOrder } from "./orders";

describe("order flow", () => {
  test("create order with valid user and product", async () => {
    // Set up test data across services
    const user = await createUser({
      email: "[email protected]",
      name: "Buyer",
    });
    
    const product = await createProduct({
      name: "Widget",
      priceCents: 1000,
      inventory: 10,
    });
    
    // Test the cross-service order creation
    const order = await createOrder({
      userId: user.id,
      productId: product.id,
      quantity: 2,
    });
    
    expect(order.totalCents).toBe(2000);
    expect(order.status).toBe("confirmed");
  });
});

Run tests with the Encore CLI:

encore test

Deployment

Deploy all services together with a single command. Encore provisions separate databases for each service, sets up networking, and configures Pub/Sub infrastructure.

git add -A
git commit -m "E-commerce microservices"
git push encore

From the Encore Cloud dashboard you can connect your AWS or Google Cloud account to deploy there. You can decide if you want to deploy all services together, or a separate independently scalable processes.

Encore Cloud dashboard

Common Patterns

API Gateway

Expose a unified API while keeping services internal. This pattern is useful when you want to aggregate data from multiple services or simplify the external API.

// gateway/gateway.ts
import { api } from "encore.dev/api";
import { users, products, orders } from "~encore/clients";

// Public endpoint that orchestrates internal services
export const checkout = api(
  { expose: true, method: "POST", path: "/checkout" },
  async (req: CheckoutRequest) => {
    const user = await users.get({ id: req.userId });
    const product = await products.get({ id: req.productId });
    const order = await orders.create({
      userId: req.userId,
      productId: req.productId,
      quantity: req.quantity,
    });
    
    return {
      orderId: order.id,
      userName: user.name,
      productName: product.name,
      total: order.totalCents,
    };
  }
);

Saga Pattern

For operations that span multiple services and need rollback on failure. This ensures consistency even when individual steps can fail.

export const checkout = api(
  { expose: true, method: "POST", path: "/checkout" },
  async (req: CheckoutRequest) => {
    // Step 1: Reserve inventory
    await products.reserveInventory({
      id: req.productId,
      quantity: req.quantity,
    });
    
    try {
      // Step 2: Charge payment
      await payments.charge({
        userId: req.userId,
        amountCents: totalCents,
      });
    } catch (error) {
      // Rollback step 1 if payment fails
      await products.releaseInventory({
        id: req.productId,
        quantity: req.quantity,
      });
      throw error;
    }
    
    // Step 3: Create order (only if payment succeeded)
    return orders.create(req);
  }
);

When to Split Services

Start with fewer, larger services. Split when you have a clear reason:

  1. Team boundaries: Different teams own different services
  2. Deployment independence: One part changes frequently, another is stable
  3. Scaling needs: One service needs 10x the resources
  4. Fault isolation: A failure in one area shouldn't affect others

Don't split just because "microservices are better." Every service boundary adds operational complexity. Start simple, split when the pain of not splitting outweighs the cost.

Ready to build your next backend?

Encore is the Open Source framework for building robust type-safe distributed systems with declarative infrastructure.