we run into following problem, maybe you can give us some adivce or best practice:
We use many indices (80) and for search we use one alias to query all of them at the same time as search results can be in found in any index and should be returned together.
The reason for this many indices is that every index has different fields, so using only one index (e.g. with different types) would result in sparsity and a huge number of fields ( > 1.000) (which is not recommented by Elastic).
However, with using many indices our search perfomance is very poor (around 5 - 10 seconds).
Any advice on this? Is it bad to use so many indices and adress all together in one search? Any other hints where to look to improve search performance?