There’s a config property for Spring Boot management.metrics.distribution.percentiles
the type of a value of the property is Map<String, double[]>

e.g. it may be set as following:

management.metrics.distribution.percentiles:
   all: 0.5, 0.95

the questions are:

1. what are some other common keys (like key=all) for the entries of this map? like can one restrict percentiles to http server requests only?
2. and where to look for them? (maybe some source code references?)
3. how can one define custom keys