Entry Microservices Interview Questions

Microservices architecture structures an application as a collection of small, independently deployable services. Each service handles a specific business capability and can be developed, deployed, and scaled individually.

Monolithic apps are tightly coupled and deployed as a single unit. Microservices break the system into small independent services with separate deployments. Microservices offer better scalability and fault isolation.

Key advantages include independent deployment, fault isolation, easier scaling, technology flexibility, and faster development cycles through small focused teams.

Microservices introduce distributed system complexity, data consistency issues, operational overhead, and challenges in monitoring, logging, and networking.

Service discovery enables dynamic locating of service instances. It may be client-side or server-side using tools like Eureka, Consul, or Zookeeper for registry and lookup.

An API Gateway is the single entry point for client requests. It handles routing, authentication, rate limiting, caching, and protocol translation. Examples include Kong, Zuul, and NGINX.

Synchronous communication uses REST or gRPC. Asynchronous communication uses queues like Kafka or RabbitMQ. The choice depends on latency and resilience needs.

Each service owns its own database to maintain autonomy. Distributed transactions are managed via sagas or event-driven approaches to ensure consistency.

Synchronous services wait for responses (REST). Asynchronous services communicate without waiting using message brokers. Async improves resilience but adds complexity.

Eventual consistency allows data to be temporarily inconsistent across services but ensures it becomes consistent over time. Techniques include CQRS, event sourcing, and sagas.

The circuit breaker prevents cascading failures by stopping calls to a failing service. It opens when failures exceed a threshold and resets after the service recovers. Tools include Hystrix and Resilience4j.

Load balancing distributes traffic across multiple service instances. It improves performance and fault tolerance using tools like NGINX, HAProxy, or Envoy.

Security includes authentication (OAuth2, JWT), authorization, TLS communication, API Gateway enforcement, and service-to-service authentication.

Centralized logging (ELK), monitoring (Prometheus, Grafana), and distributed tracing (Jaeger, Zipkin) help troubleshoot and monitor microservices health.

Microservices are packaged into Docker containers for portability and consistency. Orchestration tools like Kubernetes manage scaling, networking, and deployments.

Kubernetes automates deployment, scaling, self-healing, load balancing, and service discovery for containerized microservices using declarative YAML configurations.

By deploying multiple instances, using load balancing, automatic failover, and stateless services with resilient storage. Ensures minimal downtime.

Sagas coordinate distributed transactions by using a sequence of local transactions. If one step fails, compensating actions revert previous changes.

Services communicate through events using message brokers like Kafka or RabbitMQ. Event-driven architecture improves decoupling, scalability, and resilience.

Microservices scale horizontally by adding instances. Orchestrators like Kubernetes distribute traffic across instances using load balancing.