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hash-db
Experimental distributed pseudomultimodel keyvalue database (it uses python dictionaries) imitating dynamodb querying with join only SQL support, distributed joins and simple Cypher graph support and document storage
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InfluxDB
Power Real-Time Data Analytics at Scale. Get real-time insights from all types of time series data with InfluxDB. Ingest, query, and analyze billions of data points in real-time with unbounded cardinality.
Not an expert on Iron Maiden (I do enjoy various metal/heavy rock) but just a casual read through Wikipedia doesn't scream "music theory as the cornerstone of their success". A forced analogy that I think does not really stand on its feet.
I disagree with the premise that there's some crystal ball that those companies have which tells them that asking those questions somehow determines good candidates. It's more likely that it actually filters for the type of person who is willing to do his homework and has a good baseline of discipline and is willing to prepare. Which arguably is has some value in itself.
I don't have a formal CS degree but I have studies implemented data structures/algos and spent quite a bit of time (months) to make them performant inside a database. I can guarantee you that the knowledge that you will ask for in a whiteboard interview is ways less than one percent of what's required to implement performant and practically useable data structures for use in modern programming languages and databases.
And the punchline is that in reality it is all about the seeming minutia that the author is dismissive about. The reality is that the market for simple, generalist solutions in terms of programming languages and databases is zero. There's a ton of optimizations and literally HACKS (for a lack of a better) word that make real-world data structures and altos go fast. Just take a look here and tell me how many platform-specific things you can find (this is bulk of the implementation of persistent immutable maps for Clojure): https://github.com/clojure/clojure/blob/master/src/jvm/cloju...
Regular whiteboard datastructure/algo questions are nothing more than regurgitating 1970s theoretical solutions without much practical day-to-day value. Is there a hint of a knowledge you can extract by knowing them? Sure. Is it much more than that? I don't think so.
I am interested in database internals. Btrees come up with regard to designing database systems that are efficient to query on disk. Postgres uses them for its indexes. Radix trees are memory efficient tries which are useful for answering prefix queries. They're also called prefix trees. I use them to get a list of prefixes of a string. Useful for simple intellisense style forms or dynamodb style querying. I've also been studying LSM trees which are used in Leveldb and RocksDB.
I experiment with database technology in my experimental project hash-db https://github.com/samsquire/hash-db The code should be readable.
I need to change my search tree to be self balancing currently it grows to the left or right without balancing. I think I need to use tree rotation depending on which branch has the highest height.