Memcached Interview Questions and Answers for freshers

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100 Memcached Interview Questions and Answers for Freshers

  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. How does Memcached work?

    • Answer: Memcached stores data in memory. When a web application needs data, it first checks Memcached. If the data is present (a cache hit), it's retrieved quickly. If not (a cache miss), the application fetches it from the database, stores it in Memcached, and then returns it to the user. This process significantly reduces database load and improves response times.

  3. What are the benefits of using Memcached?

    • Answer: Benefits include faster website loading times, reduced database load, improved scalability, and enhanced application performance.

  4. What kind of data can be stored in Memcached?

    • Answer: Memcached stores key-value pairs. The keys are strings, and the values can be any kind of serialized data (e.g., strings, integers, objects serialized into JSON or other formats).

  5. Explain the concept of a "cache hit" and "cache miss" in Memcached.

    • Answer: A cache hit occurs when Memcached finds the requested data in its memory. A cache miss happens when the data is not found in Memcached, requiring a fetch from the database or another data source.

  6. What is the role of a Memcached server?

    • Answer: A Memcached server is the process that runs Memcached and manages the storage and retrieval of data. Multiple clients can connect to a single server, or a cluster of servers can be used for scalability.

  7. How does Memcached handle data expiration?

    • Answer: Memcached allows you to set an expiration time for cached items. After the expiration time, the data is automatically removed from the cache.

  8. What is the difference between Memcached and Redis?

    • Answer: While both are in-memory data stores, Redis offers more data structures (lists, sets, sorted sets) than Memcached's simple key-value store. Redis also offers persistence options, whereas Memcached's data is typically volatile (lost on server restart).

  9. How does Memcached handle data eviction?

    • Answer: When memory is full, Memcached uses Least Recently Used (LRU) algorithm to evict the least recently accessed items to make space for new data.

  10. What are some common use cases for Memcached?

    • Answer: Common use cases include caching session data, caching database queries, caching frequently accessed website content, and speeding up API responses.

  11. Explain the concept of consistent hashing in Memcached.

    • Answer: Consistent hashing improves scalability and minimizes data movement when adding or removing servers in a Memcached cluster. It uses a hash function to distribute keys across servers, minimizing the impact of changes to the server pool.

  12. How do you monitor Memcached performance?

    • Answer: Tools like `telnet` (to connect and issue commands directly to the server), and dedicated monitoring systems can be used to check metrics such as cache hit rate, memory usage, and request throughput.

  13. What are some common Memcached commands?

    • Answer: Common commands include `set` (store a value), `get` (retrieve a value), `add` (store only if the key doesn't exist), `replace` (replace an existing value), `delete` (remove a key), `incr` (increment a numeric value), and `decr` (decrement a numeric value).

  14. How can you improve Memcached performance?

    • Answer: Performance can be improved by optimizing key selection, using appropriate data serialization, tuning server settings (e.g., memory allocation), and using a cluster for distributed caching.

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