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Replica Consistency Router

Route reads across primary and replicas while respecting lag, freshness contracts, failover, and workload isolation.

Concept
Read replicas and consistency-aware routing
Difficulty
Advanced
Play time
8-12 minutes
Path
Database Reliability

Interactive scenario

Playable game area: Make the next backend decision

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Concept notes

Why this decision matters

Replica Consistency Router is focused practice for Read replicas and consistency-aware routing. It explains why each answer is safe, risky, or production-ready.

Route each read according to the consistency it actually requires.

Learning objectives

  • Route by freshness requirements.
  • Evaluate failover using replay position.
  • Isolate analytical and customer workloads.

How to play

  1. Inspect lag and product requirements.
  2. Select a routing or failover action.
  3. Balance correctness, throughput, and recovery.

Scoring

  • Correct routing actions add 250 points.
  • Risky routes reduce simulation indicators.
  • A perfect run scores 1,000.

Backend concept notes

A replica is useful only when its observed freshness meets the request contract.

Failover and analytics isolation require operational evidence.

Common mistakes

  • Routing every read to the nearest replica.
  • Calling replication a backup.
  • Promoting without comparing replay position.

Review misses from this game

Related Backend Study Lab tools

Use tools from the main site when you want to inspect real inputs.

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Scaling Intermediate

Load Balancer Challenge

Route simulated traffic across backend servers using round robin, weighted round robin, least connections, and random strategies.

Time
6-10 minutes
Concept
Load balancing strategies
  • Production Reliability
  • load balancing
  • scaling
  • latency
Play Load Balancer Challenge
Databases Intermediate

Recovery Objective Drill

Translate RPO and RTO into backup, point-in-time recovery, restore testing, and isolation decisions.

Time
7-10 minutes
Concept
Database backup and restore objectives
  • Database Reliability
  • backups
  • rpo
  • rto
Play Recovery Objective Drill

FAQ

Short answers for how this game fits backend interview and study practice.

Can a replica provide read-your-writes?

Yes, when routing waits for or proves the replica has reached the required write position.

Why isolate analytics?

Long queries can increase lag and customer latency on a shared replica.

Leaderboard

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