MySQL DBA Interview Questions and Answers for 5 years experience

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MySQL DBA Interview Questions (5 Years Experience)

  1. What is the difference between InnoDB and MyISAM storage engines?

    • Answer: InnoDB supports transactions, row-level locking, and foreign keys, making it suitable for applications requiring data integrity and concurrency. MyISAM uses table-level locking, is faster for read-heavy workloads but lacks transactional capabilities.

  2. Explain the concept of indexing in MySQL. What are different types of indexes?

    • Answer: Indexes are data structures that improve the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Different types include B-tree (most common, for range queries), full-text (for searching text), hash (for equality lookups), spatial (for geographic data).

  3. How do you monitor MySQL server performance? What tools do you use?

    • Answer: I use tools like MySQL Workbench's Performance Schema, `mysqltuner-perl`, `pt-query-digest`, and slow query logs. I monitor key metrics like CPU usage, memory usage, I/O wait, query execution times, and connection counts. I also analyze slow query logs to identify performance bottlenecks.

  4. Explain the process of MySQL replication. What are the different replication topologies?

    • Answer: MySQL replication involves copying data from a master server to one or more slave servers. This ensures high availability and scalability. Common topologies include master-slave, master-master, and multi-source replication. Each topology offers different benefits regarding redundancy and read/write performance.

  5. How do you optimize MySQL queries for performance?

    • Answer: Optimization involves analyzing query execution plans using `EXPLAIN`, adding indexes, optimizing table structures, using appropriate data types, rewriting inefficient queries, and employing caching mechanisms.

  6. What are different types of MySQL backups and when would you use each?

    • Answer: Full backups (entire database), incremental backups (changes since last full or incremental), and logical backups (copying database files). Full backups provide a complete snapshot, incrementals are faster and save space, and logical backups are useful for specific data restoration.

  7. How do you handle deadlocks in MySQL?

    • Answer: Deadlocks occur when two or more transactions are blocked indefinitely, waiting for each other to release locks. I handle them by analyzing the deadlock logs, optimizing queries to reduce lock contention, and using appropriate transaction isolation levels.

  8. Explain different transaction isolation levels in MySQL.

    • Answer: Read Uncommitted, Read Committed, Repeatable Read, Serializable. Each level offers a different balance between concurrency and data consistency. Choosing the right level depends on the application's requirements.

  9. What is the difference between a primary key and a unique key?

    • Answer: A primary key uniquely identifies each row in a table and cannot contain NULL values. A unique key also ensures uniqueness but allows NULL values (only one NULL is allowed).

  10. How do you troubleshoot a slow MySQL query?

    • Answer: I use `EXPLAIN` to analyze the query plan, check for missing indexes, optimize the query itself, analyze server resource usage, and look for I/O bottlenecks.

  11. How do you manage MySQL user accounts and permissions?

    • Answer: Using the `GRANT` and `REVOKE` statements, I create users, assign roles, and control access to specific databases, tables, and columns based on the principle of least privilege.

  12. What is MySQL's binary log and how is it used?

    • Answer: The binary log records all data-modifying statements. It's crucial for replication and point-in-time recovery. Analyzing it can help track database changes.

  13. Describe your experience with MySQL performance tuning. Give specific examples.

    • Answer: [Describe specific scenarios, like optimizing a slow query by adding an index, resolving I/O bottlenecks, or improving query execution plans. Quantify results – e.g., "Reduced query execution time from 10 seconds to 0.5 seconds".]

  14. How do you handle high availability and disaster recovery for MySQL?

    • Answer: [Describe replication strategies, clustering, backups, and recovery procedures. Mention specific tools used like MySQL Group Replication or Galera Cluster.]

  15. Explain your experience with MySQL partitioning.

    • Answer: [Describe different partitioning strategies and when they're appropriate, along with examples of when you used partitioning to improve performance or manageability.]

  16. How do you secure a MySQL server?

    • Answer: [Detail security measures, such as strong passwords, access control lists, disabling remote root access, regular security audits, and keeping the server and software up-to-date.]

  17. What is your experience with MySQL replication setup and troubleshooting?

    • Answer: [Detail experience with setting up master-slave, master-master, or other replication topologies. Describe troubleshooting scenarios like replication lag or replication errors.]

  18. Describe your experience with database schema design.

    • Answer: [Describe your approach to database design, including normalization, data modeling, and the use of ER diagrams. Provide examples of database schemas you've designed.]

  19. How do you handle large datasets in MySQL?

    • Answer: [Discuss techniques such as partitioning, indexing, query optimization, and potentially using tools like MySQL Cluster or sharding for extreme scalability.]

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