Database Questions and Answers Commonly Asked in FAANG Interviews

 Preparing for FAANG interviews can feel overwhelming, especially when it comes to core computer science subjects like databases. Whether you are an aspiring backend engineer, data engineer, or full stack developer, your understanding of database systems plays a major role in technical evaluations. These companies evaluate not only your theoretical knowledge but also your ability to apply concepts under pressure. In this blog, we will walk through the most important database interview questions and answers that often appear in FAANG-level interviews. This guide will help you strengthen your fundamentals, structure your preparation better, and feel more confident during discussions.

Why FAANG Focuses Strongly on Databases

FAANG companies operate on massive data volumes and require highly optimized systems. Their backend architecture depends on robust databases, scalable storage mechanisms, and efficient data retrieval. This is why the database interview questions and answers you encounter are designed to check whether you understand reliability, consistency, distributed design, and performance optimization. Strong database fundamentals show that you can build systems that scale to millions of users while ensuring speed and accuracy.

Key Concepts FAANG Interviewers Expect You to Know

Before diving into the actual questions, it’s important to understand what FAANG engineers want to evaluate. They generally look for clarity on:

• How well you understand SQL and NoSQL databases

• Your ability to choose and justify the right data model

• Knowledge of ACID properties and consistency models

• Familiarity with indexing, replication, and sharding

• Comfort with writing optimized queries

• Understanding of transaction management and concurrency

Once these foundations are clear, the database interview questions and answers usually revolve around deeper concepts that indicate real-world readiness.

Common Database Questions and Answers for FAANG Interviews

1. What are the main differences between SQL and NoSQL databases?

FAANG companies rely on both relational and non-relational databases depending on the product and use case. SQL databases are structured, follow a rigid schema, and support ACID transactions. They are ideal for systems that require strict consistency. NoSQL databases, on the other hand, offer flexibility, horizontal scalability, and schema-less structures. They are typically preferred for large-scale distributed systems and high-speed data ingestion. Understanding the trade-offs between both is essential during interviews.

2. What are ACID properties and why are they important?

ACID stands for Atomicity, Consistency, Isolation, and Durability. These properties guarantee reliable transaction execution. Atomicity ensures all parts of a transaction succeed or fail together. Consistency ensures data moves from one valid state to another. Isolation prevents concurrent transactions from interfering with each other. Durability ensures data remains intact even after system failures. FAANG companies emphasize these properties because they build mission-critical systems that cannot risk data corruption.

3. What is indexing and how does it improve query performance?

Indexing is a mechanism that improves the speed of data retrieval by creating a reference structure separate from the main data. When indexing is implemented properly, the database engine is able to locate rows faster instead of scanning the entire table. However, indexes also come with overhead since they require additional storage and slower write operations. Interviewers expect you to explain not only what indexing is but also when it should or should not be used.

4. What is normalization and why is it used?

Normalization is a technique used to structure a relational database in a way that reduces redundancy and preserves data integrity. It involves breaking down large tables into smaller ones and establishing clear relationships. The goal is to avoid anomalies during insert, update, or delete operations. While normalized databases improve consistency, highly normalized designs may reduce performance. FAANG interviews may also test your awareness of when to denormalize for efficiency.

5. What are transactions and how do they work in a DBMS?

A transaction is a sequence of operations that are treated as a single unit. Transactions help maintain data integrity and ensure that the database remains consistent even in the event of errors or failures. During interviews, you are often assessed on concepts like commit, rollback, and savepoints. Demonstrating a clear understanding of transaction isolation levels also reflects your ability to handle concurrency issues.

6. What is sharding in distributed databases?

Sharding refers to splitting large datasets into smaller parts (shards) stored across multiple servers. This helps in scaling horizontally and improving parallel processing. FAANG systems handle petabytes of data, so sharding becomes essential for minimizing latency and ensuring high availability. Interviewers may further explore how shard keys are selected and how uneven data distribution is managed.

7. What is replication and why is it used?

Replication involves maintaining multiple copies of the same dataset across different servers. It improves data availability and fault tolerance. If one server fails, another replica can immediately take over. In interviews, you may be asked to describe synchronous vs asynchronous replication and the trade-offs between consistency and performance.

8. What is the difference between primary and foreign keys?

A primary key uniquely identifies each record in a table. A foreign key establishes a relationship between two tables by referencing a primary key of another table. Understanding this relationship is crucial in designing relational models. Interviewers typically check whether you understand referential integrity and cascading operations as well.

9. What is a deadlock and how can it be prevented?

A deadlock occurs when two or more transactions block each other indefinitely by holding resources the other needs. Preventing deadlocks requires thoughtful transaction sequencing, locking strategies, and timeout mechanisms. FAANG interviewers may also ask about detecting deadlocks using wait-for graphs or cycle detection.

10. What are the different types of joins in SQL?

Joins are used to retrieve data from multiple tables based on logical relationships. The main types include inner join, left join, right join, and full join. Understanding each join type helps demonstrate your ability to write efficient and meaningful queries. Interviewers also assess whether you understand cross joins and self-joins and how they impact query performance.

Final Thoughts

The database interview questions and answers asked in FAANG interviews are meant to evaluate practical understanding, system design thinking, and your ability to optimize data interactions at scale. A strong grasp of these core concepts helps you stand out in technical rounds and gives you the confidence to express your reasoning clearly. While the questions may appear simple on the surface, the depth of your explanation often determines whether you move forward. Strengthening your fundamentals, thinking about data from a system-wide perspective, and practicing your articulation will significantly increase your chances of success.