1. What are Microservices?
Answer
Microservices is an architectural style where an application is divided into small, independent services, each responsible for a single business capability, communicating via lightweight protocols (e.g., REST, gRPC, messaging).
2. What are the main benefits of Microservices?
Answer
Scalability (independent scaling of services)
Faster deployment (CI/CD friendly)
Technology flexibility (polyglot)
Resilience (failure isolation)
Better team ownership (service per team)
3. Difference between Monolith and Microservices?
Answer
Monolith → Single large codebase, tightly coupled, difficult to scale.
Microservices → Distributed, loosely coupled, independently deployable.
4. How do Microservices communicate?
Answer
Synchronous: REST, gRPC
Asynchronous: Message brokers (RabbitMQ, Kafka, Azure Service Bus)
5. What is API Gateway in Microservices?
Answer
API Gateway acts as an entry point for all requests, handling routing, load balancing, security, rate limiting, and logging. Example: Kong, NGINX, Azure API Management.
6. How do you handle service discovery?
Answer
Client-side: Eureka, Consul
Server-side: API Gateway + Load Balancer (e.g., Kubernetes Services, AWS ALB)
7. What is Circuit Breaker Pattern?
Answer
It prevents repeated calls to a failing service. If a service fails continuously, the breaker "opens" and stops traffic until it recovers. Example: Polly (.NET), Hystrix (Java).
8. What is the Saga Pattern in Microservices?
Answer
Saga manages distributed transactions by breaking them into smaller local transactions.
Choreography: Events trigger the next action.
Orchestration: Central controller manages flow.
9. How do you ensure data consistency in Microservices?
Answer
Event-driven design (event sourcing, Kafka)
Saga pattern
Idempotency in APIs
Eventual consistency
10. How do you handle the database per microservice?
Answer
Each microservice owns its own database to avoid coupling. For queries across services → use CQRS, API Composition, or Database Views.
11. What is CQRS?
Answer
Command Query Responsibility Segregation separates read (queries) and write (commands) models for performance and scalability.
12. What is Event Sourcing?
Answer
Instead of storing only the final state, every change is stored as an event. The state is rebuilt by replaying events. Useful for audit logs and financial transactions.
13. How do you secure Microservices?
Answer
OAuth2 + JWT for authentication
API Gateway for centralized security
Mutual TLS for service-to-service security
14. What is Service Mesh?
Answer
Service mesh (e.g., Istio, Linkerd) provides traffic management, security, observability, and service discovery between services without changing code.
15. How do you achieve resilience in Microservices?
Answer
Retry policy
Circuit breaker
Bulkhead isolation
Timeout handling
Load balancing
16. How to handle logging in Microservices?
Answer
Use centralized logging:
ELK Stack (Elasticsearch, Logstash, Kibana)
Azure Application Insights
Grafana + Loki
17. How do you handle monitoring in Microservices?
Answer
Metrics: Prometheus, Azure Monitor
Tracing: Jaeger, OpenTelemetry
Dashboards: Grafana
18. What is the role of Docker in Microservices?
Answer
Docker packages microservices into portable containers, ensuring consistency across environments.
19. What is Kubernetes in Microservices?
Answer
Kubernetes orchestrates containers, providing scaling, load balancing, auto-healing, and service discovery.
20. How do you achieve scalability in Microservices?
Answer
Horizontal scaling (replica sets in Kubernetes)
Load balancers
Auto-scaling policies (HPA, cluster autoscaler)
21. How do you handle inter-service communication failure?
Answer
Retry policies
Circuit breaker
Fallback responses
Dead-letter queues for failed messages
22. How do you test Microservices?
Answer
Unit Tests (per service)
Contract Testing (e.g., Pact)
Integration Testing (with dependencies)
End-to-End Testing
23. What are some design patterns in Microservices?
Answer
API Gateway
Saga Pattern
Circuit Breaker
Database per Service
Event Sourcing
Strangler Fig (migration)
24. What is the Strangler Fig Pattern?
Answer
It helps migrate from monolith to microservices gradually by building new services around old ones and slowly decommissioning the monolith.
25. What is Blue-Green Deployment?
Answer
Deploy new version in parallel (Green), keep old version (Blue). Switch traffic once stable. Ensures zero downtime.
26. What is Canary Deployment?
Answer
Release a new version to a small subset of users before rolling out to all.
27. How do you handle configuration in Microservices?
Answer
Use Centralized Config Management:
Spring Cloud Config, Azure App Configuration, Consul KV, Kubernetes ConfigMaps & Secrets.
28. What are the common challenges in Microservices?
Answer
Distributed data management
Debugging & tracing
Network latency
Deployment complexity
Security & governance
29. What is the difference between Orchestration and Choreography?
Answer
Orchestration: Central controller dictates workflow.
Choreography: Services react to events without central control.
30. How do you migrate from a Monolith to Microservices?
Answer
Identify bounded contexts (Domain-Driven Design)
Apply the Strangler Fig pattern
Extract services one by one
Introduce API Gateway gradually
Ensure monitoring & observability
Amit Kumar SinghPosted Sep 7, 2025, 1:06 PM
Thank you for Informative Knowledge.