How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a medium difficulty System Design question, commonly asked during Technical Screen rounds at LinkedIn.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at LinkedIn during technical interviews.

Explain database transactions and ACID | LinkedIn Interview Question

Quick Overview

This question evaluates a candidate's understanding of database transactions including ACID properties, isolation levels (read uncommitted, read committed, repeatable read, serializable), common anomalies (dirty reads, non-repeatable reads, phantom reads), MVCC, and commit/rollback semantics, testing competency in transactional correctness and concurrency control. Commonly asked in System Design and database contexts because it probes reasoning about data integrity, visibility, and durability under concurrent workloads, and it tests both conceptual understanding of transactional guarantees and practical application of isolation behavior in relational database systems.

Database Transactions and ACID under Concurrency

Prompt

You are working with a relational database that supports transactions and multiple isolation levels. Explain:

The ACID properties of transactions:
- Define atomicity, consistency, isolation, and durability.
How common isolation levels differ and which anomalies they prevent:
- Isolation levels: read uncommitted, read committed, repeatable read, serializable.
- Anomalies: dirty reads, non-repeatable reads, phantom reads.
How commits and rollbacks work in practice (including the effect on visibility and durability).
How MVCC (multi-version concurrency control) helps achieve isolation.
Provide a concrete example:
- A simple schema.
- A sequence of statements from two concurrent sessions that demonstrates correct transactional usage under concurrency (i.e., no anomalies), and briefly explain why it works.

Assume a mainstream RDBMS (e.g., PostgreSQL or MySQL/InnoDB). If behavior differs by engine, note the typical difference briefly.

Explain database transactions and ACID

Quick Overview