DynamoDB is a NoSQL database. It has built-in security and in-memory cache for internet scale applications.
DynamoDB scales according to your demand and maintains response times under ten milliseconds at any scale. For applications that require a response time in microseconds, DynamoDB Accelerator (DAX) provides a fully managed in-memory cache.
Using DynamoDB saves you the trouble of managing and maintaining servers. Moreover, DynamoDB offers availability and fault-tolerance.
By default, DynamoDB secures your data by encrypting it.
DynamoDB is used by famous companies like:
Samsung
Netflix
Lyft
To learn more, refer to their official website.