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Home/Questions/SQL/Explain the concept of ACID properties in the context of databases.

Explain the concept of ACID properties in the context of databases.

SQLeasy0.4 min read

**ACID**: Atomicity (all or nothing), Consistency (valid state transitions), Isolation (concurrent transactions don't interfere), Durability (committed data persists). **Why it matters**: Without ACID, financial and operational data become inconsistent; retries and failures...

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Frequency
Low
Asked at 4 companies
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
AccentureCognizantEPAMYash Technologies
Interview Pro Tip

Red Flag: Parroting definitions without trade-offs. Pro-Move: Contrast ACID in OLTP vs. eventual consistency in distributed systems, and why Delta Lake added ACID to lakes.

Why This Question Matters

This easy-level SQL question appears frequently in data engineering interviews at companies like Accenture, Cognizant, EPAM, and 1 others. While less common, it tests deeper understanding that distinguishes strong candidates.

How to Approach This

Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.

Expert Answer
87 words

ACID: Atomicity (all or nothing), Consistency (valid state transitions), Isolation (concurrent transactions don't interfere), Durability (committed data persists). Why it matters: Without ACID, financial and operational data become inconsistent; retries and failures create duplicates or lost updates. Scalability trade-off: Strict isolation (e.g., Serializable) limits throughput; most OLTP systems use Read Committed or Repeatable Read. Cost: ACID adds overhead (locking, WAL); eventual consistency systems avoid it for scale but require application-level handling. Modern context: Delta Lake, Iceberg bring ACID to data lakes; critical for upserts and concurrent writes.

The complete answer continues with detailed implementation patterns, architectural trade-offs, and production-grade considerations covering performance optimization and real-world examples.

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According to DataEngPrep.tech, this is one of the most frequently asked SQL interview questions, reported at 4 companies. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.

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