nosql databases

• data represented in a key-value store, document store, or graph database.
• data is denormalized.
• joins are done in application code.
• favors eventual-consistency.
  • in terms of cap-theorem, nosql favors availability over consistency.

types of nosql databases

key-value store

• basically a hashmap.
• backed by memory, and allows for $O(1)$ reads and writes.
• keys can be maintained in order.
• often used for caching.

document-database

graph-database

wide column store

• basically a nested hashmap.
• examples include bigtable, hbase, and cassandra.
• high availability and high scalability.
• normally used for very large datasets.

references

• https://en.wikipedia.org/wiki/Key-value_database