Microservicessystem_design~12 mins

Feature flags in Microservices - Architecture Diagram

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System Overview - Feature flags

This system manages feature flags to enable or disable features dynamically in a microservices environment. It allows safe rollout, testing, and rollback of features without redeploying services.

Key requirements include low latency flag checks, centralized control, and consistency across services.

Architecture Diagram

User
  |
  v
Load Balancer
  |
  v
API Gateway
  |
  +-------------------+
  |                   |
  v                   v
Feature Flag Service  Microservices
  |                   |
  v                   |
Cache (Redis)          |
  |                   |
  v                   v
Database (Feature Flags Store)

Components

User

client

End user making requests to the system

Load Balancer

load_balancer

Distributes incoming requests evenly to API Gateway instances

API Gateway

api_gateway

Routes requests to microservices and feature flag service

Feature Flag Service

service

Manages feature flag states and evaluates flags for microservices

Microservices

service

Application services that check feature flags to enable/disable features

Cache (Redis)

cache

Stores feature flag states for fast access to reduce database load

Database (Feature Flags Store)

database

Persistent storage of feature flag configurations and rules

Request Flow - 10 Hops

User → Load Balancer

Load Balancer → API Gateway

API Gateway → Microservices

Microservices → Feature Flag Service

Feature Flag Service → Cache (Redis)

Cache (Redis) → Feature Flag Service

Feature Flag Service → Microservices

Microservices → API Gateway

API Gateway → Load Balancer

Load Balancer → User

Failure Scenario

Component Fails:Cache (Redis)

Impact:Feature Flag Service cannot retrieve cached flag states, causing increased latency and load on the database.

Mitigation:Feature Flag Service falls back to querying the database directly. Cache is rebuilt asynchronously. Database replication ensures availability.

Architecture Quiz - 3 Questions

Test your understanding

Which component is responsible for deciding if a feature is enabled for a user?

AFeature Flag Service

BLoad Balancer

CAPI Gateway

DCache (Redis)

Design Principle

This architecture uses a centralized Feature Flag Service with caching to provide fast, consistent feature flag evaluations across microservices. The cache reduces database load and latency, while the load balancer and API Gateway ensure scalable and secure request routing.