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HLDsystem_design~12 mins

Data replication strategies in HLD - Architecture Diagram

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System Overview - Data replication strategies

This system explains common data replication strategies used to improve data availability, fault tolerance, and read performance in distributed systems. It covers synchronous and asynchronous replication methods, showing how data is copied from a primary database to one or more replicas.

Architecture Diagram
User
  |
  v
Load Balancer
  |
  v
Primary Database (Master)
  |           \
  |            \---> Replica 1 (Slave)
  |            \
  |             \---> Replica 2 (Slave)
  |
  v
Cache
  |
  v
Application Server
Components
User
client
Initiates requests to the system
Load Balancer
load_balancer
Distributes incoming requests to the primary database or replicas
Primary Database (Master)
database
Main data store where writes happen and data is replicated from
Replica 1 (Slave)
database_replica
Read-only copy of primary database for load distribution and fault tolerance
Replica 2 (Slave)
database_replica
Additional read-only copy for scalability and availability
Cache
cache
Stores frequently accessed data to reduce database load and latency
Application Server
service
Processes business logic and serves responses to users
Request Flow - 8 Hops
User → Load Balancer
Load Balancer → Primary Database (Master)
Primary Database (Master) → Replica 1 (Slave)
Primary Database (Master) → Replica 2 (Slave)
Load Balancer → Replica 1 (Slave)
Replica 1 (Slave) → Cache
Cache → Application Server
Application Server → User
Failure Scenario
Component Fails:Primary Database (Master)
Impact:Writes fail and data replication stops; reads can continue from replicas but may be stale
Mitigation:Promote a replica to primary using failover mechanisms; use replication logs to catch up replicas
Architecture Quiz - 3 Questions
Test your understanding
Which component handles write requests in this replication strategy?
AReplica 1 (Slave)
BPrimary Database (Master)
CCache
DLoad Balancer
Design Principle
This architecture demonstrates how data replication improves system availability and read scalability by copying data from a primary database to multiple replicas. It balances consistency and performance using synchronous or asynchronous replication methods.