Datadog Backend Developer interview questions

I have applied online. I have received the invitation for intro meeting in 3 days and the Tech Source. She asked for my experience, my previous projects and the tech stack I have worked on. She was very curious to about the product and asked me to explain the flow of the product. Datadog is very flexible with my 3 month notice period and they have also given me the choice of work locations to choose from. I have received an invitation for second round (first technical). This interview is with one of the team members and based on leetcode style easy-medium range problems. I was given 1 hour for two problems. I have to explain my algorithm and why I have chosen the specific data structures and the time complexities. I was not able to manage the second problem.

First interview with HR then moved on to live coding challenge using Coderpad.io, HR said it would be LeetCode type challenge but it was more difficult than that. Next steps would be of three more technical interviews