ElastiCache: Redis

Redis, expands to Remote Dictionary Server

• It is a fast, open-source, in-memory key-value data store
• Can be used as
  • a database
  • cache
  • message broker
  • queue
• The project started by Salvatore Sanfilippo, to improve scalability of his Italian startup.
• Redis delivers sub-millisecond response times
• Enables millions of requests per second
• Good for real-time applications in
  • Gaming
  • Ad-Tech
  • Financial Services
  • Healthcare
  • IoT
• Popular choice for
  • Caching
  • session management
  • gaming
  • leaderboards
  • real-time analytics
  • geospatial
  • ride-hailing
  • chat/messaging
  • media streaming
  • pub/sub apps.

Redis in Brief

• All Redis data resides in-memory
• Hence, Redis avoid seek time delays
• Can access data in microseconds.
• Redis features
  • versatile data structures
  • high availability
  • geospatial
  • Lua scripting
  • Transactions
  • on-disk persistence
  • cluster support
  • simpler to build real-time internet scale apps.

Redis data types

• Strings – text or binary data up to 512MB in size
• Lists – a collection of Strings in the order they were added
• Sets – an unordered collection of strings with the ability to intersect, union, and diff other Set types
• Sorted Sets – Sets ordered by a value
• Hashes – a data structure for storing a list of fields and values
• Bitmaps – a data type that offers bit level operations
• HyperLogLogs – a probabilistic data structure to estimate the unique items in a data set

Redis Cluster and Shard

• A Redis shard (or a node group in the API and CLI) is a grouping of 1 to 6 related nodes.
• A Redis (cluster mode disabled) cluster always has one shard.
• A Redis (cluster mode enabled) cluster can have 1–90 shards.
• A multiple node shard implements replication by have one read/write primary node and 1–5 replica nodes.
• A Redis cluster is a logical grouping of one or more ElastiCache for Redis Shards.
• Data is partitioned across the shards in a Redis (cluster mode enabled) cluster.