bluebird promise concurrency - SERP Analysis

http://bluebirdjs.com/docs/api/promise.map.html

https://stackoverflow.com/questions/24745455/how-to-use-the-bluebird-concurrency-option-for-the-map-function

https://badgerbadgerbadgerbadger.medium.com/concurrency-control-in-promises-with-bluebird-977249520f23

http://bluebirdjs.com/docs/api/promise.all.html

https://github.com/petkaantonov/bluebird/issues/708

https://www.zleptnig.com/blog/the-power-of-bluebirds-promise-map

http://bluebirdjs.com/docs/api/promise.mapseries.html

http://bluebirdjs.com/docs/api/promise.each.html

https://blog.jasonkim.ca/post/resolving-bluebird-promises-with-concurrency

https://medium.com/better-programming/implement-your-own-bluebird-style-promise-map-in-js-7c081b7ad02c