I usually got this error:
# Error establishing a Redis connection `read error on connection to 127.0.0.1:6379` WordPress is unable to establish a connection to Redis. This means that the connection information in your `wp-config.php` file are incorrect, or that the Redis server is not reachable. * Is the correct Redis host and port set? * Is the Redis server running? If you need help, please read the [installation instructions](https://github.com/rhubarbgroup/redis-cache/blob/develop/INSTALL.md). To disable Redis, delete the `object-cache.php` file in the `/wp-content/` directory.
And when I refresh the browser, it back to normal. Seems, Redis unable to hand much requests and traffic