Redis, MemCached (Memory)
When you want to build a leaderboard or need a real-time application.
ELK/ EFK Stacks
If you need high performing searches and cataloging ElasticSearch based stack for collecting large sets of streams and unstructured information.
InfluxDB (TimeSeries)
If your information has a lot of timestamps (eg. IoT).
Ledger (Blockchain-like Transaction Secure Database)
If you cannot afford to have your data tampered in any way.
DynamoDB (KeyValue)
If your application requires real-time transactions (eg. bidding or high volume on-line purchases).
