When I switched to working on search my boss had written "Search Engines: Information Retrieval in Practice" and I found it very helpful for wrapping my head around the different subsystems that make up search. It took me about a month to work through and it's only $16 on Amazon

[1] https://amzn.to/3dW5YBQ

Great post. I'm working on another open source search engine on top of Redis (http://redisearch.io), mostly focused on index building and serving, and real-time updates of the data. The part about queries being highly varying is extremely challenging. You have to deal with simple "foo bar" queries and complex queries with intricate filtering and crazy stuff (I have a user doing an AND intersection of 17 OR unions, each of 32 terms, while checking the ordering of term offsets!). It's super fun to work on this stuff.

Another recommended book that was not mentioned in the post: Search Engines: Information Retrieval in Practice https://www.amazon.com/Search-Engines-Information-Retrieval-...