Anti-corruption layer in Microservices - System Design Exercise

Design: Anti-corruption Layer for Microservices Integration

Design the anti-corruption layer component between two microservices with different domain models and communication protocols. Out of scope: internal implementation of each microservice business logic.

Functional Requirements

FR1: Allow two or more microservices with different data models and protocols to communicate without corrupting each other's domain logic

FR2: Translate requests and responses between incompatible interfaces

FR3: Prevent changes in one service from forcing changes in others

FR4: Support synchronous and asynchronous communication

FR5: Handle data validation and transformation

FR6: Log translation errors for debugging

Non-Functional Requirements

NFR1: Must handle up to 10,000 requests per second

NFR2: API response latency p99 under 150ms

NFR3: Availability target 99.9% uptime

NFR4: Must be scalable horizontally

NFR5: Should not introduce tight coupling between services

Think Before You Design

Questions to Ask

❓ Question 1

❓ Question 2

❓ Question 3

❓ Question 4

❓ Question 5

❓ Question 6

Key Components

Translator/Adapter modules for data transformation

Facade or Gateway to expose unified interface

Validation components to check data correctness

Error handling and logging mechanisms

Communication protocols (REST, gRPC, message queues)

Caching if needed for performance

Design Patterns

Adapter pattern to convert interfaces

Facade pattern to provide simplified interface

Anti-corruption Layer pattern from Domain-Driven Design

Message translation in asynchronous messaging

Circuit breaker for fault tolerance

Reference Architecture

Client Service A  <--->  Anti-Corruption Layer  <--->  Service B

+----------------+       +-------------------------+       +----------------+
| Service A      |       | Anti-Corruption Layer    |       | Service B      |
| (Domain Model) | <---> | - Translator/Adapter     | <---> | (Different     |
|                |       | - Validator             |       |  Domain Model) |
|                |       | - Facade/Gateway        |       |                |
+----------------+       +-------------------------+       +----------------+

Components

Translator/Adapter

Custom code in microservice language (e.g., Java, Node.js)

Convert data formats and models between Service A and Service B

Facade/Gateway

REST API or gRPC endpoint

Expose a unified interface to Service A and hide complexity of Service B

Validator

Validation libraries or custom logic

Ensure data integrity and correctness before forwarding

Error Logger

Centralized logging system (e.g., ELK stack, Splunk)

Record translation and communication errors for troubleshooting

Communication Layer

REST/gRPC clients or message queue clients

Handle protocol-specific communication with Service B

Request Flow

1. Service A sends a request to the Anti-Corruption Layer facade.

2. Facade receives the request and passes it to the Translator.

3. Translator converts Service A's data model to Service B's model.

4. Validator checks the transformed data for correctness.

5. If valid, Communication Layer sends the request to Service B.

6. Service B processes and sends a response back.

7. Communication Layer receives response and passes it to Translator.

8. Translator converts response back to Service A's model.

9. Facade returns the translated response to Service A.

10. Errors during translation or communication are logged.

Database Schema

No dedicated database for the anti-corruption layer is required. It acts as a stateless translator and proxy. If caching is added, a simple key-value store schema may be used to cache frequent translations.

Scaling Discussion

Bottlenecks

Translator component CPU usage under high request load

Communication Layer latency due to network or Service B slowness

Error logging system overload

Single instance of Anti-Corruption Layer causing a bottleneck

Solutions

Scale Anti-Corruption Layer horizontally with load balancer

Optimize translation logic and use efficient serialization formats

Implement circuit breaker and retries to handle Service B slowness

Use asynchronous messaging to decouple and buffer requests

Use scalable logging infrastructure with backpressure handling

Interview Tips

Time: Spend 10 minutes clarifying requirements and constraints, 20 minutes designing the architecture and data flow, 10 minutes discussing scaling and trade-offs, 5 minutes summarizing.

Explain the purpose of the anti-corruption layer to protect domain integrity

Discuss how translation and validation prevent corruption

Describe synchronous and asynchronous communication handling

Highlight scalability and fault tolerance considerations

Mention patterns like Adapter and Facade to simplify integration