docs: protected Client getClient(String apiKey) throws SQLException {
          Client client;
          synchronized (mutex) {
              client = clientCache.get(apiKey);
          }
  
          if (client == null) {
              client = super.getClientInternal(apiKey);
              synchronized (mutex) {
                  if (client != null) {
                      clientCache.put(apiKey, client);
                  }
              }
          }
  
          return client;
      }