Junior Database Administrator Interview Preparation Guide (FAANG Standards)

Clear understanding of why you're pursuing this DBA role, what attracts you to this particular company, and your 2-3 year career goals. Be authentic about whether you want to specialize in database administration or explore broader infrastructure roles.

Brief overview of database technologies you've worked with (e.g., MySQL, PostgreSQL, MongoDB, Oracle, SQL Server, etc.), cloud platforms you've used (AWS RDS, Azure Database, GCP Cloud SQL), and any monitoring or backup tools you're familiar with. Prepare to discuss depth in at least one database system.

Ability to articulate your 1-2 years of DBA experience clearly, including specific database systems you've administered, key projects you've worked on, and skills you've developed. Be ready to discuss your progression from entry-level DBA work to independent task execution.

Understanding the difference between efficient and inefficient queries. Knowledge of indexes and their impact on query performance. Ability to recognize N+1 query problems, unnecessary full table scans, and suboptimal join orders. Understanding execution plans at a basic level (reading EXPLAIN output). Knowledge of when to use different approaches for the same logical result.

Ability to use subqueries in SELECT, WHERE, and FROM clauses. Understanding correlated vs. non-correlated subqueries. Proficiency with CTEs (WITH clause) for complex queries. Know when to use subqueries vs. JOINs for clarity and performance. Practice nested query problems with proper syntax and logical flow.

Mastery of GROUP BY clause, aggregate functions (COUNT, SUM, AVG, MIN, MAX), and HAVING clause for filtering grouped results. Understanding how GROUP BY interacts with NULL values, how to count distinct values, and how to perform calculations on grouped data. Practice queries that require multiple levels of aggregation.

Deep understanding of INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN operations. Know how to join multiple tables, understand join conditions, handle NULL values in joins, and recognize when to use each join type. Practice queries combining 2-4 tables with correct join logic and filtering conditions.

Ability to write basic SELECT queries with WHERE clauses, ORDER BY, GROUP BY, and HAVING. Understand filtering with multiple conditions, using operators (AND, OR, NOT, BETWEEN, IN), and aggregate functions (COUNT, SUM, AVG, MIN, MAX). Practice queries retrieving specific data from single and multiple columns with various filter conditions.

Understanding the process of planning, testing, and deploying database patches and updates. Knowledge of backup procedures before patching, post-patch verification, and rollback procedures if needed. Understanding version compatibility, deprecation notices, and breaking changes in updates. Knowledge of patch management tools and scheduling considerations for production systems.

Systematic approach to investigating common problems: slow queries, connection issues, disk space problems, long-running transactions, deadlocks, and failed jobs. Understanding how to gather diagnostic information (logs, metrics, system information) and narrow down root causes. Knowledge of basic resolution strategies for each class of issue. Understanding when to escalate vs. when to resolve independently at junior level.

Understanding key performance indicators (CPU, memory, disk I/O, connections, query response times). Knowledge of monitoring tools and how to set up alerts for anomalies. Understanding how to check database size, identify long-running queries, and monitor resource usage. Knowledge of system views/DMVs that reveal performance metrics. Ability to interpret monitoring data to identify problems early.

Understanding different backup types (full, incremental, differential), backup strategies, and recovery procedures. Knowledge of how to verify backup integrity, test recovery procedures, and restore data from backups. Understanding RPO (Recovery Point Objective) and RTO (Recovery Time Objective). Ability to discuss backup tools specific to databases you've worked with (e.g., mysqldump, pg_dump, SQL Server backup, RMAN for Oracle). Knowledge of point-in-time recovery using transaction logs.

Understanding user authentication, role-based access control (RBAC), and principle of least privilege. Knowledge of how to create users, assign permissions at database/table/column levels, and audit access. Understanding encryption at rest and in transit. Knowledge of how to disable unnecessary database accounts and remove default users. Understanding password policies and secure credential management.

Understanding various approaches to improve database performance: adding indexes, denormalization, caching strategies, query restructuring, and materialized views. Knowledge of the performance tuning cycle (identify bottleneck, measure impact, implement fix, verify improvement). Understanding when performance optimization is needed vs. premature optimization. Knowledge of query hints and optimization directives when standard optimization fails.

Ability to read and interpret EXPLAIN/EXPLAIN PLAN output. Understanding execution plans to identify sequential scans, index usage, join strategies, and sort operations. Knowledge of how to rewrite queries for better performance (eliminating OR conditions in WHERE clause, using UNION ALL instead of UNION, pushing predicates down). Understanding query statistics and their role in execution plan selection. Ability to identify obviously inefficient plans and suggest improvements.

Understanding how indexes improve query performance by reducing disk I/O. Knowledge of index types (single-column, composite, covering indexes, full-text). Understanding the tradeoff between query speed and update cost (indexes slow down INSERT/UPDATE/DELETE). Ability to identify missing indexes from slow queries. Understanding clustered vs. non-clustered indexes. Knowledge of index fragmentation and maintenance.

Understanding of normalization principles (1NF, 2NF, 3NF, BCNF) and when to apply them. Ability to design schemas that eliminate data anomalies and redundancy. Knowledge of primary keys, foreign keys, and referential integrity. Understanding when to deviate from strict normalization (denormalization for performance). Ability to identify and fix poorly designed schemas that cause data anomalies or update problems.

Understanding capacity planning basics—growth projections, performance degradation over time, and when to scale. Knowledge of vertical scaling (bigger hardware) vs. horizontal scaling (sharding, replication) and appropriate use cases. Understanding monitoring for capacity planning (disk usage growth, CPU trends). Discussion of how data volume growth affects backup times, recovery times, and maintenance windows. Realistic junior-level discussion—you're not designing global systems yet.

Understanding ACID properties (Atomicity, Consistency, Isolation, Durability) and why they matter. Knowledge of transaction isolation levels and their performance/consistency tradeoffs. Understanding how replication affects consistency guarantees. Knowledge of eventual consistency vs. strong consistency concepts. Discussion of how to handle consistency issues in distributed database scenarios.

Understanding RPO (Recovery Point Objective) and RTO (Recovery Time Objective) requirements. Ability to design backup strategies that meet RTO/RPO targets. Understanding point-in-time recovery using transaction logs. Knowledge of offsite backup storage for disaster scenarios. Understanding testing and validation of disaster recovery procedures to ensure they work when needed. Discussion of disaster recovery at appropriate junior scale.

Understanding basic replication concepts (master-slave/primary-replica, multi-master replication). Knowledge of asynchronous vs. synchronous replication tradeoffs. Understanding how replication improves availability and read scalability. Knowledge of failover mechanisms and how to handle replication lag. Discussion of replication at junior level—understanding the concepts, tools, and basic implementation for databases you've worked with (MySQL replication, PostgreSQL streaming replication, SQL Server mirroring).

Ability to explain technical concepts clearly to both technical and non-technical audiences. Examples of documenting procedures or knowledge so others can learn. Demonstration of asking clarifying questions before acting on requests. Examples of proactive communication—informing stakeholders about planned maintenance, explaining the impact of performance issues, or proposing solutions to problems.

Examples of taking responsibility for assigned DBA tasks and seeing them through to completion. Demonstration of reliability—following through on commitments, communicating proactively about issues, delivering on promises. Examples of going beyond minimum requirements to ensure tasks are done well. Understanding the importance of reliability in a role where failures can impact the entire company.

Demonstration of methodical approach to investigating database issues—gathering information, forming hypotheses, testing them, and reaching conclusions. Examples of times you've broken down complex problems into manageable steps. Showing persistence when facing unfamiliar situations. Examples of how you've improved or optimized something based on systematic analysis.

Examples of learning new database systems, technologies, or tools independently. Demonstration of asking good questions and seeking to understand not just 'how' but 'why'. Examples of mistakes you've learned from and adjustments you've made. Enthusiasm about continuous learning in the evolving database field. Showing progression from basic tasks to more complex responsibilities during your junior DBA experience.

Ability to work effectively with senior DBAs, application development teams, system administrators, and security teams. Examples of how you've supported colleagues, communicated technical information to non-technical stakeholders, and coordinated changes across teams. Understanding of how DBA work impacts other departments. Demonstration of being a reliable, responsive team member who can be counted on for assigned responsibilities.

Substantive questions you ask about the team's database environment, scale, growth trajectory, and biggest technical challenges. This demonstrates genuine interest and helps you understand what you'll be working on. Examples: 'What database systems do you primarily support?', 'What are your most critical databases?', 'What are the team's biggest performance challenges right now?', 'How often do you deal with unplanned downtime, and what are typical causes?'

Clear understanding of what you'll learn in this junior DBA role, what the career progression looks like, how the team supports learning and skill development, and what advancement opportunities exist. Discussion of mentorship—how will senior DBAs help you grow and what's expected of you as you gain experience.

Understanding how this DBA role works with other DBAs (if any), how they interface with developers and other teams, what the on-call structure looks like, and how knowledge is shared within the team. Discussion of what 'good collaboration' looks like in this specific team context. Understanding of team culture and whether it aligns with how you like to work.

Understanding of what this specific DBA role entails within this team—what are their primary database systems, what are typical day-to-day responsibilities, what are their biggest technical challenges, and how does this DBA role contribute to team success. Ability to discuss how your experience and skills align with this specific position rather than general DBA skills.