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PRANJUL RATHOUR
PRANJUL RATHOUR

Posted on Originally published at pranjulrathour.scult.in

Incremental indexing: keeping a RAG index current without re-embedding everything

#rag #indexing #maintenance

A document set that updates weekly doesn't need the whole corpus re-embedded every time — most of it hasn't changed. Re-embedding everything anyway is the default in a lot of tutorials, and it's needlessly slow and costly at any real scale.

A practical incremental approach

  1. Hash each source document (or each chunk) and store the hash alongside its embedding.
  2. On an update run, compute new hashes and diff against stored ones — only re-embed documents whose hash changed.
  3. Delete embeddings for documents that were removed entirely, not just leave them stale in the index.

The trap to avoid

Chunk boundaries can shift even for a small edit near the start of a document, which changes every downstream chunk's hash. Chunk-level hashing catches real changes; document-level hashing is simpler but coarser — pick based on how often your documents change internally versus wholesale.

See metadata filtering in RAG pipelines for a related ingestion-time concern.

About Pranjul Rathour

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Pranjul Rathour

Pranjul Rathour presenting on stage in a blue polo, with his Annapurna demo video on the screen behind him
Presenting Annapurna on stage

Pranjul Rathour giving a talk titled 'How and what I do', with demo videos of his products Vaidya and Annapurna on screen
Talking through the products he has shipped

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On the mic

Pranjul Rathour pitching with a microphone in front of a projector slide at CSJMU, Kanpur
Pitching at CSJMU, Kanpur

Pranjul Rathour is a GenAI engineer from Kanpur, India, and CTO at SCULT INDIA, currently shipping production RAG,
fine-tuning and agentic AI systems, mentoring 200+ students through TechVerse Enclave, and judging and speaking at
student hackathons across India. Updated 2026-09-11.

Reach out if you want to talk GenAI, book a campus session, or invite him to judge:

Pranjul Rathour · GenAI engineer, 3x hackathon winner, campus mentor. Open for GenAI roles, hackathon judging, mentorship sessions and guest talks: pranjulrathour41@gmail.com · Invite me to your campus
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