✅ 1. What are the key benefits and challenges of Microservices? 

✅ 2. How do microservices communicate with each other?

🔹 Two types of communication:

1. Synchronous (Request-Response)
   
   

   • REST APIs over HTTP (common)
     
     

   • gRPC (more efficient)
     
     

2. Asynchronous (Event-driven)
   
   

   • Message brokers like Kafka, RabbitMQ, ActiveMQ
     
     

🔹 Examples:

• REST: OrderService calls InventoryService via HTTP
  
  

• Messaging: UserService publishes UserCreated event to Kafka

✅ 3. What are service discovery and load balancing?

🔹 Service Discovery:

Automatically locating service instances in a dynamic environment (e.g., containers scaling up/down).

• Client-side: Client queries the registry (e.g., Netflix Eureka)
  
  

• Server-side: API Gateway or Load Balancer handles routing
  
  

🔹 Load Balancing:

Distributing traffic across multiple service instances.

✅ 5. What is the Circuit Breaker Pattern?

Used to prevent cascading failures when a dependent service is down or slow.

🔹 How it works:

• Monitor failure rate of calls to a service.
  
  

• If failures exceed a threshold, "open" the circuit.
  
  

• During open state, return fallback or error immediately.
  
  

• Retry after a cooldown period.

✅ 6. How would you secure inter-service communication? 

✅ 7. How do you handle distributed transactions or data consistency?

🔹 Challenge:

In microservices, a single logical transaction may span multiple services, but XA (2PC) is discouraged (complex, slow).

🔹 Patterns to solve this:

✅ 1. Saga Pattern (preferred)

• Sequence of local transactions with compensating actions for rollback.
  
  

• Coordination:
  
  

  • Choreography: Services emit events and listen to each other.
    
    

  • Orchestration: Central coordinator service manages steps.
    
    

✅ 2. Eventual Consistency

• Accept temporary inconsistency.
  
  

• Sync using reliable messaging (Kafka, RabbitMQ).