Definition: A database designed to store and query values recorded over time, where each value is tied to a timestamp. It is commonly used to hold metrics such as request counts, error rates and response times.
So what? It is where observability metrics live, which makes it possible to chart how a system behaves over minutes, hours or days and spot when something changes.
Example: Storing the number of failed checkout requests every few seconds so a team can see whether errors rose after a release.
