Configuration as a service

In my organization we have a micro-services architecture. Up until now, it was fairly easy to manage and work with as the configurations are rather limited, and often independent of specific tenant (we have multi-tenant system).

But recently the number of tenant specific configuration has steadily increased and we need a central service to manage all the configurations specific to each client per service.

For example, a client can have a configuration for minimum number of tokens after which classification triggers. It might be 2 for tenant A or 4+ for tenant B.

What I am looking for is if there is already an available system, which people use in production, capable enough to handle generic types of configuration? The configurations can be complex JSON structures, YAML files or something similar (note: we are willing to write the layer for transformation), java properties files, ini files etc.

We have already considered zookeeper, etcd, consul etc. as an agent and a wrapper on top of it, but we might have to store some data as well, which would cause performance issue, and overall it is not useful in our case.