Memcached Interview Questions and Answers for 10 years experience

0
100 Memcached Interview Questions & Answers

  1. What is Memcached?

    • Answer: Memcached is a high-performance, distributed memory object caching system. It's used to speed up dynamic web applications by alleviating database load.

  2. Explain the architecture of Memcached.

    • Answer: Memcached is a client-server architecture. Clients connect to one or more Memcached servers, storing and retrieving data. Servers operate independently and distribute data across multiple nodes using consistent hashing. Data is stored in memory for fast access.

  3. How does Memcached handle data expiration?

    • Answer: Memcached uses an LRU (Least Recently Used) algorithm to evict items when memory is full. You can also set an expiration time for each item. When an item expires, it's automatically removed from the cache.

  4. What are the different data types supported by Memcached?

    • Answer: Memcached primarily stores data as byte strings. While not explicitly typed, you can store various data representations (integers, strings, serialized objects) as byte strings. It's the application's responsibility to manage data type interpretation.

  5. Explain consistent hashing in Memcached.

    • Answer: Consistent hashing distributes data across multiple Memcached servers, minimizing data relocation when servers are added or removed. It uses a hash function to map keys to servers. Changes to the server pool result in only a small subset of keys needing to be redistributed.

  6. What is the difference between Memcached and Redis?

    • Answer: Memcached is primarily a key-value store focused on speed. Redis offers more data structures (lists, sets, sorted sets) and persistence options. Memcached is generally faster for simple key-value lookups.

  7. How does Memcached handle concurrency?

    • Answer: Memcached uses locking mechanisms and atomic operations to handle concurrent access to data. This ensures data consistency when multiple clients access and modify the same data simultaneously.

  8. What is the purpose of the `slab` allocation in Memcached?

    • Answer: Memcached uses a slab allocation system to manage memory efficiently. It divides memory into fixed-size chunks (slabs) to reduce fragmentation and improve memory allocation speed.

  9. Explain the concept of cache invalidation in Memcached.

    • Answer: Cache invalidation in Memcached is often handled by using expiration times or by explicitly deleting entries. There's no automatic invalidation mechanism based on changes in the underlying data source; you need to manage this in your application logic.

  10. How do you monitor Memcached performance?

    • Answer: Memcached provides statistics via telnet or using monitoring tools. Key metrics to monitor include cache hit ratio, eviction rate, and memory usage. Tools like `memcached-tool` or dedicated monitoring systems can be used.

  11. How would you troubleshoot a slow Memcached server?

    • Answer: Troubleshooting involves checking server resource usage (CPU, memory, network), examining Memcached statistics (hit ratio, eviction rate), verifying network connectivity, and checking for any errors in Memcached logs. Consider upgrading hardware, optimizing application code, or adjusting Memcached configuration.

  12. Describe a situation where Memcached might not be the best solution.

    • Answer: Memcached is not ideal for scenarios requiring persistence, complex data structures, or transactions. Databases or other caching solutions like Redis might be more appropriate for such situations.

  13. Explain how to handle data serialization in Memcached.

    • Answer: Data is stored as byte strings. Serialization methods like JSON, Protocol Buffers, or custom serialization are used to convert complex objects into byte streams before storage and vice-versa during retrieval.

  14. Discuss the trade-offs between using Memcached and a database directly.

    • Answer: Using Memcached improves application speed but adds complexity. Database access is slower, but it's simpler and provides data persistence. The choice depends on performance needs, complexity, and data persistence requirements.

Thank you for reading our blog post on 'Memcached Interview Questions and Answers for 10 years experience'.We hope you found it informative and useful.Stay tuned for more insightful content!