The 12 Query Types

https://baymard.com/blog/ecommerce-search-query-types

Good video on testing performance of elasticsearch

https://www.elastic.co/elasticon/conf/2018/sf/the-seven-deadly-sins-of-elasticsearch-benchmarking

Very good video about migration from the Amazon ES service to a self-managed cluster (with all concerns, reasons and hard decisions behind described well). Sometimes I had the feeling like that guy is telling my story.
https://www.elastic.co/elasticon/conf/2018/sf/lyfts-wild-ride-from-amazon-es-to-self-managed-elasticsearch

Some ideas on calculating trending things

https://stackoverflow.com/questions/787496/what-is-the-best-way-to-compute-trending-topics-or-tags/826509#826509

New book

New and promising search-related book was published on Manning Publications's MEAP - Deep Learning for Search

Use this free bayesian A/B testing calculator to find out if your test results are statistically significant.

Use this free bayesian A/B testing calculator to find out if your test results are statistically significant. 
https://marketing.dynamicyield.com/bayesian-calculator/

Learning to rank problems. Well explained

Learn to rank and its various optimizations - http://opensourceconnections.com/blog/2017/08/03/search-as-machine-learning-prob/

http://opensourceconnections.com/blog/2017/04/01/learning-to-rank-linear-models/

What works in e-commerce - a meta-analysis of 6700 online experiments

http://www.qubit.com/sites/default/files/pdf/qubit_meta_analysis.pdf

Good short overview of caching in modern versions of ES - Caching In Elasticsearch

On two types of suggestions

Basic overview of two types of search suggestions: content && search query based suggestions.

https://www.searchblox.com/autosuggest-search-query-based-vs-content-based

Spatial search algorithms and data scructures

https://medium.com/@agafonkin/a-dive-into-spatial-search-algorithms-ebd0c5e39d2a

How to deal with the synonyms. Awesome examples

http://opensourceconnections.com/blog/2016/12/02/solr-elasticsearch-synonyms-better-patterns-keyphrases/

Visualizing Geohash

I've rescued a lost article on visualizing geohashes

Good explanation of how the DisMax works (despite that it based on Solr, but not my favorite Elasticsearch)

http://opensourceconnections.com/blog/2013/03/07/the-anatomy-of-a-dismax-query/

There you can find some useful ideas how to combine search and graphs together to improve your relevance.

http://blog.comperiosearch.com/blog/2014/02/05/dynamic-search-ranking-using-elasticsearch-neo4j-and-piwik/ 

Very interesting article that has a link on the interesting tool.

http://lucidworks.com/blog/2016/08/17/learning-to-rank-solr/ - very interesting presentation on ranking search results (and measuring the results) on Bloomberg

http://lucidworks.com/blog/2016/08/17/learning-to-rank-solr/ - very interesting presentation on automatic ranking the search results (and measuring the results) on Bloomberg

Finding You the Best Hotel at LateRooms.com with Elasticsearch

https://www.elastic.co/blog/finding-you-the-best-hotel-at-laterooms-com-with-elasticsearch

Good overview. Some of the ideas and approaches are the same as ours.

proper sorting is not that easy

Trying to sort site-wide search results on most e-commerce sites typically end up a mess, with irrelevant search results being propelled to the top of the list as users sort by price, customer ratings, etc

http://baymard.com/blog/faceted-sorting