What is a Key Value Database/Store?

Data System Architecture


A key-value database / store is a NoSQL database based on the key-value data that is stored in

You store some data, called a value, inside a key. The data can later be retrieved by key.

Each value is not limited to primitive data type but also a complex one such as list, hashes.


  • shopping cart
  • session service.



Cache library

Cache library may implement an on-disk representation (ie serialization, read-through, write-through). Be careful that you may not want any purge to happen.

There are 2 configurations/patterns:

  • Cache-Aside: Check the cache for an entry, if empty, check the system-of-record
// Pseudocode for reading values
v = cache.get(k)
if(v == null) {
    v = sor.get(k)
    cache.put(k, v)
// Pseudocode for writing values
v = newV
sor.put(k, v)
cache.put(k, v)
  • Cache-As-Sor: The cache is the system-of-record. The application accesses only the cache and the cache access the backend system-of-record via:
    • read-through to load data
    • write-through (sync) or write-behind (async) to write data


  • Java Map Cache:
    • Ehcache 1)
    • Infinispan 2), uses caffeine 3).
    • Not Caffeine. Caffeine is on-heap caching and does not offer persistence

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