Hands on phone screen, dealing with code and how to modify binary search to skip empty strings, etc.

Then, how cache works using a hashmap and how to optimize and prune based on oldest entries.

In addition, make sure you know how to iterate over a hashmap, how to update and delete, and the overall complexity of using a hashmap.

You have 5 horses racing. There are 10 sensors that measure each time a horse crosses the line. The client wants to ask: what are the fastest horses in order, based on timestamp?

What data structures would you use, and how would you update them so that you can easily ask: "Give me the top 5 horses as of now," and return those in the proper timestamp order, fastest to slowest?

Which data structures would you use, and how would you optimize for both updates and the question asked earlier?