ES 5.x drops the scroll-scan search type. This was originally deprecated in 2.1 [1] released in Nov 2015
The recommended approach is to use a scroll request that sorts documents in _doc order. Such sorts have been optimised to provide the same performance characteristics as the former scan search type. However this optimisation presumably only applies from versions 2.1. Earlier versions should work, but could be much slower. Dropping official support for earlier versions would allow us to make the change without worrying about the performance impact. The alternative is to provide configurable behaviour. There may be other reasons to bump the minimum supported version further. Note: there will be no further releases of the 1.7 line after 1.7.6, released in Nov 2016 [3] [1] https://www.elastic.co/guide/en/elasticsearch/reference/2.1/breaking_21_search_changes.html#breaking_21_search_changes [2] https://www.elastic.co/blog/elasticsearch-2-1-0-and-2-0-1-released [3] https://www.elastic.co/blog/category/releases
