Tutorials System Design Tutorial
Availability Engineering — Complete Guide
Availability Engineering — Complete Guide: free step-by-step lesson with examples, common mistakes, and interview tips — part of System Design Tutorial on Toolliyo Academy.
On this page
System Design Tutorial · Lesson 7 of 100
Availability Engineering
Basics → Scale → Interview
Basics · 1 — Building blocks · ~6 min · Module 1: System Design Foundations
What is this?
Availability is the share of time the system successfully serves requests. You raise it with redundancy, health checks, graceful degradation, and fast failover.
Why should you care?
ShopNest downtime is lost GMV. Even “read-only mode” beats a full outage during a sale.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
Availability ≈ uptime / total time
99.9% ≈ 43 min downtime/month
ShopNest levers:
multi-AZ API + health checks
degrade: disable recommendations if that service dies
keep checkout path aliveRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Nines are budgets.
- Spend redundancy on the money path first.
- Degrade non-critical features before failing the whole site.
Practice next
- Write a target like 99.9% for checkout.
- List two features ShopNest can turn off under stress.
- Add a health endpoint to your API sketch.
- Compute allowed downtime for 99.99%.
- Draw a “checkout-only” emergency mode.
Remember
Availability is a measurable budget. Redundancy + health checks. Degrade non-critical paths first.
Sale-day degrade switch
ShopNest disables personalized feed when CPU spikes.
Outcome: Checkout stays up; homepage is simpler but alive.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
Sign in to ask a question or upvote helpful answers.
No questions yet — be the first to ask!
