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Transactions & ACID

Technology Fundamentals

Transactions & ACID

1 min readPublished 22 Jul 2026

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A transaction groups several operations so they succeed or fail as one unit — essential when correctness matters (think a bank transfer).

Interactive explainer

Transactions & ACID

How databases guarantee reliable, consistent changes.

1Atomicity2Consistency3Isolation4Durability

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Atomicity

All or nothing.

Every operation in the transaction succeeds (COMMIT) or none do (ROLLBACK). A bank transfer never debits one account without crediting the other.

Check your understanding

1. What does atomicity guarantee?

2. Which property ensures committed data survives a crash?

Keep learning

Transactions & ACIDIntroduction to NoSQL Microsoft DP-900
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ACID

  • Atomicity — all steps happen, or none do (COMMIT or ROLLBACK).
  • Consistency — the database moves from one valid state to another, respecting constraints.
  • Isolation — concurrent transactions don't corrupt each other's view of the data.
  • Durability — once committed, changes survive a crash.

A transfer that debits one account must credit the other — a transaction ensures you never lose money to a half-finished operation. This is why relational databases are trusted for critical data, and a key contrast with many NoSQL systems.

Interview Intelligence

How this topic actually shows up in interviews — and how to demonstrate you understand it.

Why employers ask about this

ACID is what makes databases trustworthy for money and critical data — a classic interview topic.

Technical questions
Explain ACID with the example of a bank transfer.+

Atomicity ensures debit+credit both happen; isolation stops interference; durability keeps it after a crash.

Behavioural questions
Describe ensuring correctness in something you built.+

Show grouping related steps so a partial failure can't leave bad state.

Real-world scenarios
“Two operations must both succeed or neither.”+

Expected answer: Wrap them in a transaction — COMMIT only if both succeed, ROLLBACK on any failure.

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Employability Intelligence

Where this knowledge takes you — the jobs, skills and certifications it feeds into.

Relevant roles
Backend DeveloperDatabase AdministratorData Engineer
Skills you're proving
TransactionsACIDConsistency
Recommended certifications
Microsoft DP-900 (Data Fundamentals)Oracle / SQL certifications
Career progression

Databases & SQL → developer/DBA roles.

What employers expect

That you can design a sensible schema and write correct, efficient SQL.

Frequently asked questions

What is a database transaction?

A group of operations treated as a single unit that either all commit or all roll back.

What does ACID stand for?

Atomicity, Consistency, Isolation and Durability — the guarantees of reliable transactions.

What is the difference between COMMIT and ROLLBACK?

COMMIT makes the transaction's changes permanent; ROLLBACK undoes them entirely.

Related guides

Databases & SQL Fundamentals: Design, Query & Manage DataRelational Databases & SQL FundamentalsDatabase Design & NormalizationPrimary Keys, Foreign Keys & Relationships

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