Tutorials System Design Tutorial
Load Balancers in Production — Complete Guide
Load Balancers in Production — 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 12 of 100
Load Balancers in Production
Basics → Scale → Interview
Basics · 1 — Building blocks · ~6 min · Module 2: Networking and Traffic Management
What is this?
A load balancer spreads traffic across healthy instances and terminates client connections so you can scale APIs horizontally.
Why should you care?
Four ShopNest API pods without an LB leave clients guessing which IP to hit.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
Client → LB (health /readyz) → API1
→ API2
→ API3
Algorithms: round-robin | least-conn | sticky (sessions)
L7 LB can route /checkout to checkout poolRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Health checks remove bad nodes.
- L4 balances TCP; L7 understands HTTP paths.
- Sticky sessions help stateful apps but hurt perfect scale-out.
Practice next
- Draw ShopNest LB in front of three APIs.
- Choose least-conn for long checkout requests.
- Define a /health that fails when DB is down (or not — debate).
- Route /payments to a smaller hardened pool.
- Add connection draining for deploys.
Remember
LB enables horizontal scale. Health checks are mandatory. L7 routing unlocks pool splits.
ShopNest public ALB
ALB fronts API pods with /readyz checks.
Outcome: Bad deploys leave the pool automatically.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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