The namespace RedisRateLimitStore prepends to every key when no keyPrefix is supplied.

The two sibling Redis stores in this framework both namespace and both say why in their own source — cache-plugin's takes a prefix as a REQUIRED constructor argument, and session-plugin's CacheSessionStore defaults one so that a clear() from elsewhere cannot sign everybody out. The rate limiter's keys are the most generic of the three (the literal string anonymous for unidentified callers) and it had none.