面试题与答案

Memcached stores key-value pairs in memory to reduce the need for repeated database queries. It uses a simple and efficient hashing algorithm for distributed caching across multiple servers.

Memcached uses a time-based expiration mechanism. Each key-value pair has a specified expiration time, and once the time is reached, the data is automatically evicted from the cache.

Memcached uses slab allocation to efficiently manage memory. It categorizes memory into slabs based on size, and each slab contains items of a specific size range.

CAS is a mechanism in Memcached that allows for atomic updates. It checks if the value has been modified since it was retrieved, and updates it only if no changes occurred in the meantime.

Memcached slabs represent chunks of memory allocated for items, and classes are sets of slabs with similar-sized items. Slabs are organized into classes to efficiently manage memory usage.

Memcached replication involves creating copies of data on multiple Memcached servers. It provides redundancy and high availability in case a server goes down.

Memory optimization in Memcached can be achieved through techniques like slab reassignment, adjusting item size, and optimizing key storage.

LRU (Least Recently Used) is a caching eviction algorithm used by Memcached to remove the least recently accessed items from the cache when it reaches its memory limit.

Memcached performance can be monitored using tools like memcached-tool, telnet, or specialized monitoring software. Key metrics include hit rate, miss rate, and memory usage.

Memcached connection pooling involves reusing existing connections instead of creating new ones for each request. This helps reduce overhead and improve performance.

Memcached supports UDP (User Datagram Protocol) for fast and lightweight data transfer. It is often used for non-critical operations like cache updates.

Memcached uses a consistent hashing algorithm to determine the server responsible for a particular key. This ensures even distribution of keys across multiple servers.

The slab growth factor in Memcached determines how much the memory allocation size should grow when the existing slabs are full. It helps in efficient memory management.