Tutorials System Design Tutorial
Transactions in Distributed Systems — Complete Guide
Transactions 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 29 of 100
Transactions in Distributed Systems
Basics → Scale → Interview
Basics · 1 — Building blocks · ~6 min · Module 3: Database Systems
What is this?
Distributed transactions span services or databases. Classic 2PC is hard at scale; most teams use sagas, outbox, and idempotent local transactions instead.
Why should you care?
ShopNest checkout touches order, payment, and inventory — a single ACID transaction across all three rarely exists.
See it live — copy this example
Sketch the architecture on paper. These lessons focus on concepts and trade-offs.
Local ACID in Order DB: create order=PENDING
Then async:
Payment capture (idempotent)
Inventory reserve (idempotent)
Mark order PAID / CANCELLED with saga stepsRun Example »
This lesson uses terminal or setup steps. Run commands on your computer — the live editor appears on coding lessons.
What happened?
- Keep strong transactions inside one database.
- Coordinate across services with sagas and reliable messaging rather than fragile global 2PC.
Practice next
- Identify ShopNest steps that must be local ACID.
- Sketch a saga for pay + reserve.
- Add compensation: release stock if pay fails.
- Write the cancel path when payment declines.
- Store saga state explicitly.
Remember
Local ACID + saga across services. Idempotency is mandatory. Avoid naive global transactions.
Checkout saga
ShopNest coordinates pay and stock without 2PC.
Outcome: Failures end in cancel/release, not silent inconsistency.
Interview prep for this lesson
Practice these questions aloud after reading—each links to a full structured answer.
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