@Override
  public ByteBuffer processCommand(RequestReader request, Protocol protocol, Cache cache) {
    if (protocol == Protocol.ASCII) {
      return processAsciiCommand(request.getRequest(), cache);
    }
    // binary protocol has cas in regular add/put commands
    throw new IllegalStateException();
  }
"cas" is a check and set operation which means "store this data but only if no one else has
updated since I last fetched it."
geode-memcached/src/main/java/org/apache/geode/internal/memcached/commands/CASCommand.java