Microservicessystem_design~12 mins

Event store concept in Microservices - Architecture Diagram

Choose your learning style9 modes available

Learn Why Deep Arch Practice Challenge Design Recall Scale

System Overview - Event store concept

An event store system records all changes in the form of events. It supports microservices by storing events as the source of truth. Key requirements include reliable event storage, event replay, and supporting asynchronous communication between services.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  v
Command Service ---> Event Store ---> Event Bus ---> Multiple Microservices
                              |
                              v
                        Snapshot Store

Components

User

client

Initiates commands or queries to the system

Load Balancer

load_balancer

Distributes incoming requests evenly to API Gateway instances

API Gateway

api_gateway

Routes requests to appropriate services and handles authentication

Command Service

service

Receives commands, validates them, and writes events to the event store

Event Store

database

Stores all events in an append-only log for durability and replay

Event Bus

message_queue

Publishes events asynchronously to interested microservices

Multiple Microservices

service

Consume events to update their own state or trigger actions

Snapshot Store

database

Stores periodic snapshots of state to speed up event replay

Request Flow - 7 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Command Service

Command Service → Event Store

Event Store → Event Bus

Event Bus → Multiple Microservices

Multiple Microservices → Snapshot Store

Failure Scenario

Component Fails:Event Store

Impact:New events cannot be stored, causing command failures; event replay and state recovery are blocked

Mitigation:Use replication and backups for event store; fallback to read-only mode from snapshots and caches; alert operators for quick recovery

Architecture Quiz - 3 Questions

Test your understanding

Which component ensures commands are evenly distributed to avoid overload?

ALoad Balancer

BEvent Bus

CSnapshot Store

DAPI Gateway

Design Principle

This architecture uses event sourcing to store all changes as events in an append-only log. It decouples command processing from state updates by asynchronously publishing events via an event bus. Snapshots optimize recovery by reducing replay time. Load balancing and API gateway ensure scalability and security.