Tutorials System Design Tutorial
Fault Tolerance in Distributed Systems — Complete Guide
Fault Tolerance in Distributed Systems — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of System Design Tutorial on Toolliyo Academy.
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System Design Tutorial · Lesson 9 of 100
Fault Tolerance in Distributed Systems
Basics → Scale → Interview
Basics · 1 — Building blocks · ~6 min · Module 1: System Design Foundations
What is this?
Fault tolerance means the system keeps working (maybe degraded) when disks, nodes, or dependencies fail.
Why should you care?
Something always fails during ShopNest peak. Users should still browse and preferably still pay.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
Patterns:
Timeout + retry with jitter
Circuit breaker on Inventory
Bulkhead: separate thread pool for Payment
Replica: read from secondary if primary lag OK
ShopNest: if Recs fail → empty shelf, not 500 homepageRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Timeouts stop hung threads.
- Circuit breakers stop hammering a sick dependency.
- Bulkheads isolate failure.
- Replicas cover node loss.
Practice next
- Add timeouts to every ShopNest outbound call.
- Pick one dependency for a circuit breaker.
- Separate pools for payment vs catalog calls.
- Simulate Inventory 100% errors and watch homepage behavior.
- Add jitter to retry backoff.
Remember
Assume dependencies fail. Timeout, break, isolate, fallback. Keep core flows alive.
Inventory circuit open
ShopNest opens the inventory circuit during a bad deploy.
Outcome: Catalog still loads; add-to-cart shows “stock unknown — try again.”
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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