Elasticsearch is great and magical, but there are a bunch of defaults that you MUST set for it to be useful. I'm surprised github wasn't using these, actually (like allocating the min and max memory to be the same size).
Generally it takes a catastrophic failure under load for you to discover that 'everyone' (everyone else) uses these!
Generally it takes a catastrophic failure under load for you to discover that 'everyone' (everyone else) uses these!