Elrond has 2 layers of REST APIs that can be publicly accessed. Both of them can be recreated by anyone that wants to have the same infrastructure, but self-hosted.
These 2 layers of REST APIs are:
https://gateway.elrond.com: the lower level layer (backed by
Elrond Proxy) that handles routing all the requests in accordance to the sharding mechanism. More details can be found here.
https://api.elrond.com: the higher level layer (backed by
api.elrond.comrepository) that uses the gateway level underneath, but also integrates Elasticsearch (historical) queries, battle-tested caching mechanisms, friendly fields formatting and so on. More details can be found here.