MySQL DBA Interview Questions and Answers for 7 years experience

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MySQL DBA Interview Questions and Answers

  1. What are the different storage engines available in MySQL and their characteristics?

    • Answer: MySQL offers several storage engines, each with strengths and weaknesses. InnoDB is the default and supports transactions, ACID properties, and row-level locking, making it suitable for applications requiring data integrity. MyISAM is faster for read-heavy workloads but lacks transaction support. Memory is entirely in-memory, extremely fast but volatile. Others include Archive (for archiving data), Blackhole (discards all data), and Federated (for accessing remote MySQL servers). The choice depends on the application's specific needs.

  2. Explain the difference between MyISAM and InnoDB.

    • Answer: MyISAM is a non-transactional engine, offering faster read speeds but no support for transactions, row-level locking, or foreign keys. InnoDB is a transactional engine providing ACID properties, row-level locking, and foreign key constraints, making it suitable for applications requiring data integrity and concurrency control. MyISAM uses table-level locking, leading to potential blocking during updates, while InnoDB uses row-level locking, minimizing blocking.

  3. How do you optimize MySQL queries?

    • Answer: Query optimization involves several techniques: using EXPLAIN to analyze query execution plans, creating indexes on frequently queried columns, optimizing table structures, rewriting queries for better performance, using query caching, and tuning server parameters like buffer pool size and query cache size. Analyzing slow query logs is crucial to identify performance bottlenecks.

  4. What are indexes and how do they work?

    • 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. They work by creating a sorted structure (B-tree is common) that allows the database to quickly locate rows based on specific column values, avoiding full table scans.

  5. Explain different types of indexes in MySQL.

    • Answer: Common index types include B-tree indexes (most common, for equality and range searches), fulltext indexes (for searching text data), hash indexes (faster for equality searches but no range searches), spatial indexes (for geographic data), and composite indexes (on multiple columns).

  6. How do you monitor MySQL performance?

    • Answer: MySQL performance monitoring involves using tools like MySQL Workbench's Performance Schema, the slow query log, and system monitoring tools (like `top` or `htop` on Linux). Key metrics to track include CPU usage, memory usage, I/O wait time, query execution times, and connection counts. Tools like Prometheus and Grafana can visualize and alert on performance issues.

  7. What is the MySQL slow query log and how do you use it?

    • Answer: The slow query log records queries that take longer than a specified threshold. It helps identify performance bottlenecks by showing which queries are slow and allowing analysis of their execution plans to pinpoint areas for optimization. It's configured in the MySQL server configuration file (my.cnf or my.ini).

  8. Explain different types of MySQL backups.

    • Answer: Common backup methods include logical backups (using `mysqldump`), physical backups (copying the data files directly), and point-in-time recovery (using binary logs). Logical backups are easily manageable but slower, physical backups are faster but can be less portable, and point-in-time recovery allows restoring to a specific point in time.

  9. How do you perform a MySQL replication setup?

    • Answer: MySQL replication involves setting up a master server and one or more slave servers. The master server replicates its binary log to the slave servers, ensuring data consistency across multiple servers. This improves availability and scalability. The setup involves configuring replication parameters on both master and slave servers and involves choosing between asynchronous and synchronous replication based on requirements.

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