public synchronized void clear() {
    acceptedSpanCount.set(0);
    traceIdToTraceIdTimestamps.clear();
    spansByTraceIdTimestamp.clear();
    serviceToTraceIds.clear();
    serviceToRemoteServiceNames.clear();
    serviceToSpanNames.clear();
    autocompleteTags.clear();
  }
This is an index of {@link Span#remoteServiceName()} by {@link Endpoint#serviceName() service
name}
zipkin/src/main/java/zipkin2/storage/InMemoryStorage.java