Alex ChernyshAlex ChernyshAI Systems Engineer · Tel Aviv
Writing

Notes

Notes on AI systems, retrieval, and the work that starts after the demo.

Notes on retrieval, evals, observability, and the engineering that starts once the demo is the easy part.

2 posts
Feb 24, 2026
6 min read

Which Query Transformation Techniques Actually Help RAG?

HyDE, query rewrite, decomposition, step-back prompting, and fusion for RAG: which query transformation technique fixes which retrieval failure, and when the extra latency pays off.

+2
Feb 12, 2026
5 min read

Most RAG Failures Start in the Documents

Chunking, titles, metadata, parent-child structure, reranking, and corpus QA for RAG systems.

+2