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Really enjoyed your post. I had a question about your usage of ProxySQL.

1) Do you have to update the ProxySQL configuration on your application servers when you do a slave promotion or is that handled automatically?

2) I didn't fully understand how you know which database host has a shard (i.e. shard 22). Is that also part of your ProxySQL configuration?

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1) We actually keep the "state" for slave/master in EC2 tags, which are changed via a different mechanism.

2) There's a different configuration for mapping which database hosts exist on which shard. Our system currently has multiple database shards per machine, and that's stored in a configuration that our automation will update when new machines/shards go into production.

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