Some Good Tech References ‐ Tech Interview preparation materials for Software Engineers

their deep dives are good for basic understandings - https://www.hellointerview.com/learn/system-design/deep-dives/elasticsearch

System Design - https://github.com/donnemartin/system-design-primer

For SE principles (basics) - https://github.com/indy256/Full-stack-Developer-Interview-Questions-and-Answers