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Memcached Interview Questions and Answers: As the demand for scalable and high-performance web applications continues to grow, Memcached has become a popular choice for developers. Memcached is an open-source, distributed memory caching system that is used to speed up dynamic web applications by reducing the number of database requests. If you’re looking to land a job in web development, it’s important to have a solid understanding of Memcached. And for your sake, we have come up with Latest Memcached Interview Questions and Memcached Interview Questions for Freshers as well.
★★ Latest Technical Interview Questions ★★
Memcached Technical Interview Questions
To help you prepare for your next interview, we’ve compiled a list of the top 100 Memcached interview questions and answers, including the latest Memcached technical interview questions and those suitable for freshers. Go through the Memcached Technical Interview Questions on to learn more about Memcached and ace your next interview.
Top 100 Memcached Interview Questions and Answers 2023
1. What is Memcached?
Answer: Memcached is a freely available, open-source, high-speed, distributed memory object caching system that serves as a general-purpose tool. Its primary purpose is to enhance the performance of database-driven websites by caching data and objects in RAM for a specific duration, ranging from 1 hour to several days. When integrated with an application, it temporarily stores the data, allowing for faster access and improved performance.
2. In which language Memcached is written and who is the author?
Answer: Memcached is a software system that is coded in the “C” programming language. Brad Fitzpatrick is the original creator of this system, having developed it in 2003. Initially intended for LiveJournal, it has since been adopted by many other high-profile organizations, including Facebook, Twitter, Wikipedia, YouTube, Netlog, and Flickr.
3. What is the use of Memcached?
Answer: Memcached is used to improve the performance of web applications by reducing the load on the database and application servers.
4. How does Memcached work?
Answer: Memcached works by storing frequently accessed data in memory. When a client requests data, Memcached checks if it is available in memory. If it is, the data is returned to the client. If it is not, the data is fetched from the database and stored in memory for future requests.
5. What are the drawbacks/ limitations of Memcached?
Answer: The limitations or drawbacks of Memcached are:
- Memcached cannot store data persistently and permanently.
- Memcached is not application specific.
- Memcached cannot cache large objects.
- Memcached is not fault-tolerant or highly available.
- Memcached is not a database. It stores only temporary data.
6. What is the difference between Memcached and Redis?
Answer: Memcached is a simple key-value store, while Redis is a data structure server that supports different data types such as strings, hashes, lists, sets, and sorted sets.
7. How is Memcached different from traditional databases?
Answer: Memcached is a caching layer that stores frequently accessed data in memory, while traditional databases store data on disk. Memcached is faster than traditional databases for read-heavy workloads because it reduces the load on the database and application servers.
8. What is the syntax to store data in Memcached?
Answer: The syntax to store data in Memcached is as follows:
| set key flags exptime bytes [noreply]\r\n data block\r\n |
- key is the name of the key to store the data under.
- flags is an arbitrary 16-bit value that can be used to store additional metadata.
- exptime is the expiration time of the data, in seconds.
- bytes is the size of the data block, in bytes.
- data block is the actual data to be stored.
- noreply is an optional parameter that can be used to indicate that the client does not
- need a response from the server.
9. What is the maximum size of a value that can be stored in Memcached?
Answer: The maximum size of a value that can be stored in Memcached is 1 megabyte.
10. What is the difference between Memcache and Memcached?
| Memcache | Memcached |
|---|---|
| Memcache module provides handy procedural and object-oriented interface to Memcached. | Memcached is a high-performance, distributed memory object caching system. |
| The Memcache module provides a session handler (Memcache). | The Memcached provides a session handler (Memcached). |
| It is designed to reduce database load in dynamic web applications. | It is used to increase the dynamic web applications by reducing database load. It is the latest API. |
| Memcache is an extension that allows you to work through handy object-oriented (OOP’s) and procedural interfaces. | Memcached is an extension that uses the libMemcached library to provide API for communicating with Memcached servers. |
11. How does Memcached handle data consistency?
Answer: Memcached does not provide any built-in mechanisms for data consistency. It is the responsibility of the application to ensure that data consistency is maintained.
12. What is the best usage of Memcached?
Answer: Best usage of Memcached:
- It is easy to install in Windows as well as in the UNIX operating system.
- It reduces the burden of the database server.
- It facilitates you to delete one or more values.
- It provides API integration for all the major languages like Java, PHP, C/C++, Python, Ruby, Perl, etc.
- It enhances the performance of web application by caching.
- It facilitates you to update the values of keys.
13. What happens if the available memory in Memcached is exceeded?
Answer: If the available memory in Memcached is exceeded, the oldest data is evicted from the cache.
14. How does Memcached handle data expiration?
Answer: Memcached supports setting an expiration time for each key-value pair. When the expiration time is reached, the key-value pair is automatically deleted from the cache.
15. How can you monitor the performance of Memcached?
Answer: The performance of Memcached can be monitored using various tools such as Memcached-stats, Munin, and Ganglia.
16. What is the difference between a Memcached client and a Memcached server?
Answer: A Memcached client is an application that interacts with the Memcached server to store and retrieve data, while a Memcached server is a process that runs on a server and stores data in memory.
17. How can you increase the performance of Memcached?
Answer: The performance of Memcached can be increased by adding more servers to the Memcached cluster, increasing the available memory, and optimizing the application code.
18. What is the syntax to retrieve data from Memcached?
Answer: The syntax to retrieve data from Memcached is as follows:
| get key [key …]\r\n |
- key is the name of the key to retrieve data for.
- The command can be used to retrieve multiple keys at once by specifying them separated by spaces.
19. What is Memcached clustering?
Answer: Memcached clustering is the process of setting up multiple Memcached servers to work together as a single caching system.
20. How does Memcached handle concurrent access to the same key?
Answer: Memcached uses a locking mechanism to ensure that only one client can update a key-value pair at a time.
21. How can you ensure high availability for Memcached?
Answer: High availability for Memcached can be ensured by setting up a replication cluster with multiple Memcached servers.
22. What is the Memcached protocol?
Answer: The Memcached protocol is a text-based protocol that is used by Memcached clients to communicate with Memcached servers.
23. How does Memcached handle data compression?
Answer: Memcached supports data compression to reduce the memory footprint of stored data.
24. How can you configure Memcached to use SASL authentication?
Answer: Memcached can be configured to use SASL authentication by setting the appropriate configuration options and creating SASL users.
25. What is the syntax to delete data from Memcached?
Answer: The syntax to delete data from Memcached is as follows:
| delete key [exptime]\r\n |
- key is the name of the key to delete.
- exptime is an optional expiration time for the deletion, in seconds.
26. What is a Memcached slab?
Answer: A Memcached slab is a block of memory used by Memcached to store key-value pairs. Each slab is a fixed size and contains values of a specific size range.
27. How can you tune the Memcached cache size?
Answer: The Memcached cache size can be tuned by adjusting the max memory setting and the item size limits for each slab.
28. What is Memcached replication?
Answer: Memcached replication is the process of creating copies of data across multiple Memcached servers to ensure high availability and fault tolerance.
29. How does Memcached handle data consistency across replicas?
Answer: Memcached does not provide any built-in mechanisms for data consistency across replicas. It is the responsibility of the application to ensure that data consistency is maintained.
30. How can you ensure data consistency across Memcached replicas?
Answer: Data consistency across Memcached replicas can be ensured by implementing a consistency protocol such as the two-phase commit protocol.
31. How can you configure Memcached to use encryption?
Answer: Memcached can be configured to use encryption by enabling SSL/TLS and configuring the appropriate SSL/TLS options.
32. What is the Memcached memory allocation algorithm?
Answer: The Memcached memory allocation algorithm is a slab-based allocation algorithm that optimizes memory usage by allocating memory in fixed-size chunks.
33. How can you configure Memcached to use a custom memory allocator?
Answer: Memcached can be configured to use a custom memory allocator by implementing the appropriate API and configuring the Memcached options.
34. What is the syntax to increment or decrement a value in Memcached?
Answer: The syntax to increment or decrement a value in Memcached is as follows:
| incr key value\r\n decr key value\r\n |
- key is the name of the key to increment or decrement.
- value is the amount to increment or decrement the key by.
35. How does Memcached handle cache misses?
Answer: When a cache miss occurs, Memcached fetches the data from the database and stores it in the cache for future requests.
36. How can you configure Memcached to use consistent hashing?
Answer: Memcached can be configured to use consistent hashing by enabling the consistent hashing option and configuring the appropriate options.
37. What is the Memcached eviction policy?
Answer: The Memcached eviction policy determines which key-value pairs are evicted from the cache when the available memory is exceeded. The default policy is LRU (least recently used).
38. How can you configure Memcached to use a different eviction policy?
Answer: Memcached can be configured to use a different eviction policy by implementing a custom eviction algorithm and configuring the Memcached options.
39. How does Memcached handle cache invalidation?
Answer: Memcached does not provide any built-in mechanisms for cache invalidation. It is the responsibility of the application to invalidate cached data when necessary.
40. How can you implement cache invalidation in Memcached?
Answer: Cache invalidation can be implemented in Memcached by using a time-based expiration policy or by implementing a custom invalidation mechanism.
41. What is the Memcached binary protocol?
Answer: The Memcached binary protocol is a binary protocol that is used by Memcached clients to communicate with Memcached servers in a more efficient and compact form.
42. What is the syntax to check and set a value in Memcached?
Answer: The syntax to check and set a value in Memcached is as follows:
| cas key flags exptime bytes cas_unique\r\n data block\r\n |
- key is the name of the key to check and set.
- flags is an arbitrary 16-bit value that can be used to store additional metadata.
- exptime is the expiration time of the data, in seconds.
- bytes is the size of the data block, in bytes.
- cas_unique is the unique identifier for the value being checked and set.
- data block is the actual data to be stored.
- The command can be used to prevent other clients from modifying a value between the check and set operations.
43. How can you configure Memcached to use the binary protocol?
Answer: Memcached can be configured to use the binary protocol by enabling the binary protocol option and configuring the appropriate options.
44. What is the Memcached UDP protocol?
Answer: The Memcached UDP protocol is a lightweight protocol that is used by Memcached clients to send and receive data in a fire-and-forget mode.
45. How can you configure Memcached to use the UDP protocol?
Answer: Memcached can be configured to use the UDP protocol by enabling the UDP protocol option and configuring the appropriate options.
46. What is Memcached cache stampede?
Answer: Memcached cache stampede is a condition where a large number of requests are made for a key that is not present in the cache, causing a sudden surge in requests to the backend database.
47. How can you prevent Memcached cache stampede?
Answer: Memcached cache stampede can be prevented by using a time-based expiration policy or by implementing a cache fill-in strategy.
48. What is Memcached slab reassignment?
Answer: Memcached slab reassignment is a process where Memcached automatically moves data from one slab to another to optimize memory usage.
49. How can you configure Memcached to optimize slab usage?
Answer: Memcached can be configured to optimize slab usage by adjusting the item size limits and the number of slabs.
50. What is Memcached key hashing?
Answer: Memcached key hashing is the process of mapping a key to a particular server in a Memcached cluster using a hashing algorithm.
51. How can you configure Memcached key hashing?
Answer: Memcached key hashing can be configured by adjusting the hashing algorithm and the number of virtual nodes.
52. What is Memcached connection pooling?
Answer: Memcached connection pooling is a technique where Memcached clients reuse existing connections to Memcached servers to improve performance and reduce network overhead.
53. How can you configure Memcached connection pooling?
Answer: Memcached connection pooling can be configured by adjusting the maximum number of connections and the connection timeout.
54. What is Memcached session management?
Answer: Memcached session management is the process of using Memcached to store and retrieve session data in a web application.
55. How can you implement Memcached session management?
Answer: Memcached session management can be implemented by using a Memcached session handler and configuring the appropriate options.
56. What is the Memcached CAS operation?
Answer: The Memcached CAS (compare and swap) operation is a mechanism for atomic updates of key-value pairs in a Memcached cache.
57. How can you use the Memcached CAS operation?
Answer: The Memcached CAS operation can be used by implementing the appropriate Memcached client API and using the cas() method.
58. What is the Memcached append operation?
Answer: The Memcached append operation is a mechanism for appending data to the end of a value in a Memcached cache.
59. How can you use the Memcached append operation?
Answer: The Memcached append operation can be used by implementing the appropriate Memcached client API and using the append() method.
60. What is the Memcached prepend operation?
Answer: The Memcached prepend operation is a mechanism for prepending data to the beginning of a value in a Memcached cache.
61. How can you use the Memcached prepend operation?
Answer: The Memcached prepend operation can be used by implementing the appropriate Memcached client API and using the prepend() method.
62. What is the Memcached touch operation?
Answer: The Memcached touch operation is a mechanism for updating the expiration time of a key-value pair in a Memcached cache.
63. How can you use the Memcached touch operation?
Answer: The Memcached touch operation can be used by implementing the appropriate Memcached client API and using the touch() method.
64. What is the Memcached flush operation?
Answer: The Memcached flush operation is a mechanism for clearing all data from a Memcached cache.
65. How can you use the Memcached flush operation?
Answer: The Memcached flush operation can be used by implementing the appropriate Memcached client API and using the flush() method.
66. What is Memcached binary protocol?
Answer: Memcached binary protocol is a protocol for communication between Memcached clients and servers that uses a binary format for messages.
67. What are the advantages of using Memcached binary protocol?
Answer: The advantages of using Memcached binary protocol include lower overhead, faster serialization and deserialization, and support for additional operations and features.
68. What are the advantages of using Memcached ASCII protocol?
Answer: The advantages of using Memcached ASCII protocol include ease of debugging, compatibility with a wide range of clients and servers, and support for human-readable data serialization.
69. What are the advantages of using Memcached UDP protocol?
Answer: The advantages of using Memcached UDP protocol include lower latency, reduced overhead, and improved performance for read-heavy workloads.
70. What is the Memcached TCP protocol?
Answer: The Memcached TCP protocol is a protocol for communication between Memcached clients and servers that uses the Transmission Control Protocol (TCP) for reliable, ordered delivery of messages.
71. What are the advantages of using Memcached TCP protocol?
Answer: The advantages of using Memcached TCP protocol include reliability, support for connection-oriented communication, and compatibility with a wide range of clients and servers.
72. What is the Memcached SASL API?
Answer: The Memcached SASL (Simple Authentication and Security Layer) API is an interface for implementing SASL authentication in Memcached clients and servers.
73. How can you use the Memcached SASL API?
Answer: The Memcached SASL API can be used by implementing the appropriate client and server-side functions and configuring the appropriate options.
74. What is the Memcached stats command?
Answer: The Memcached stats command is a mechanism for retrieving statistics about a Memcached server, such as the number of items in the cache, cache hits and misses, and memory usage.
75. How can you use the Memcached stats command?
Answer: The Memcached stats command can be used by sending a STATS command to the server using the appropriate client API.
76. What is Memcached caching?
Answer: Memcached caching is the process of storing frequently accessed data in a Memcached cache to reduce the amount of time it takes to access that data.
77. What are the benefits of Memcached caching?
Answer: The benefits of Memcached caching include improved performance, reduced database load, and improved scalability.
78. What are the best practices for Memcached caching?
Answer: The best practices for Memcached caching include selecting appropriate caching strategies, using consistent hashing, and monitoring and optimizing cache usage.
79. What is consistent hashing in Memcached?
Answer: Consistent hashing is a mechanism used by Memcached to ensure that the distribution of data across multiple cache servers is balanced and predictable.
80. How does consistent hashing work in Memcached?
Answer: Consistent hashing works by mapping each key in the cache to a virtual ring, which is divided into partitions. Each cache server is assigned to one or more partitions, so that each key maps to a specific server.
81. What is Memcached sharding?
Answer: Memcached sharding is the process of partitioning data across multiple cache servers to improve performance and scalability.
82. How does Memcached sharding work?
Answer: Memcached sharding works by dividing data into multiple smaller caches, or shards, and distributing those shards across multiple cache servers. Each cache server is responsible for a subset of the data.
83. What is Memcached pooling?
Answer: Memcached pooling is the process of creating and managing a pool of Memcached connections to improve performance and reduce overhead.
84. How does Memcached pooling work?
Answer: Memcached pooling works by creating a pool of connections to a Memcached server or cluster, and reusing those connections for multiple requests. This reduces the overhead of creating and tearing down connections for each request.
85. What is Memcached compression?
Answer: Memcached compression is a mechanism for reducing the size of data stored in a Memcached cache by compressing it before storage.
86. What is the maximum size of data that can be stored in Memcached?
Answer: The maximum size of data that can be stored in Memcached is 1 megabyte (MB).
87. What is the Memcached slab allocator?
Answer: The Memcached slab allocator is a memory management system used by Memcached to efficiently allocate and manage memory for cached data.
88. How does the Memcached slab allocator work?
Answer: The Memcached slab allocator works by dividing memory into fixed-size slabs, or chunks, and using these slabs to store cached data. Slabs are created dynamically based on the size of the data being stored.
89. What is Memcached eviction policy?
Answer: Memcached eviction policy is a mechanism used by Memcached to determine which items should be evicted from the cache when it becomes full.
90. What are the types of Memcached eviction policies?
Answer: The types of Memcached eviction policies include least recently used (LRU), least frequently used (LFU), and random.
91. What is the default eviction policy in Memcached?
Answer: The default eviction policy in Memcached is LRU.
92. How can you configure the eviction policy in Memcached?
Answer: The eviction policy in Memcached can be configured by setting the appropriate options when starting the Memcached server.
93. How does Memcached replication work?
Answer: Memcached replication works by creating a replica of cached data on multiple cache servers. Updates to the data are propagated to all replicas to ensure consistency.
94. What is the Memcached CAS protocol?
Answer: The Memcached CAS (Compare and Swap) protocol is a mechanism used by Memcached to ensure that only one client can modify a cached item at a time.
95. What are the limitations of Memcached?
Answer: Some limitations of Memcached include limited data durability, lack of built-in security features, and limited support for complex data types.
96. How can you ensure data durability in Memcached?
Answer: Data durability in Memcached can be ensured by using a combination of replication and persistent storage to maintain copies of cached data.
97. What are the security risks associated with Memcached?
Answer: The security risks associated with Memcached include data theft, data corruption, and denial-of-service attacks.
98. How can you secure a Memcached instance?
Answer: A Memcached instance can be secured by using authentication, encryption, and access controls to limit access to the cache.
99. What is the Memcached ASCII protocol?
Answer: The Memcached ASCII protocol is a text-based protocol used by Memcached clients to communicate with the Memcached server.
100. What are the benefits of using the Memcached binary protocol?
Answer: The benefits of using the Memcached binary protocol include improved performance, support for advanced features, and improved error handling.
The Top 100 Memcached Interview Questions and Answers provide a comprehensive overview of the key concepts and practical applications of Memcached technology, enabling candidates to prepare effectively for their interviews. We hope this article has been helpful to you. o acquire additional knowledge, please follow us on freshersnow.com.