Short answer: a title with the primary keyword, a subtitle that adds a secondary keyword, a description that repeats the keyword naturally in the first two paragraphs, the most specific categories available, and all 7 backend keyword slots used fully without repeating title words.
The 5 elements Amazon indexes
Title and subtitle: the heaviest-weighted fields for Amazon's search algorithm.
Book description: Amazon indexes it in full, so your primary keyword should appear in the first couple of paragraphs.
Categories: pick the most specific ones available, not just the biggest — it's easier to stand out in a niche category.
The 7 backend keywords: the space KDP gives you for keywords that don't appear on the cover or description but do work in search.
Author name: kept consistent across all your books so Amazon associates them together over time.
Common mistakes when filling in backend keywords
Repeating words already in the title — wasted space.
Using commas or quotation marks inside the field — Amazon handles these differently than most people expect.
Copying competitors' keywords without checking they actually describe your book.
KDP allows up to 7 backend keyword fields per book, each up to 50 characters — space many authors leave unused or poorly filled.
Official Amazon KDP documentation, 2026