---
title: "Why Is Reindexing So Important?"
author: "Elyse Munselle"
date: 2026-09-09
canonical_url: https://bonsai.io/blog/why-is-reindexing-so-important/
license: CC BY-SA 4.0
license_url: https://creativecommons.org/licenses/by-sa/4.0/
copyright: Bonsai.io, 2026
---

### The Non-Engineer’s Guide to Reindexing

If you're a product leader running search, you own the budget for it, or you just got asked "what's our AI plan," you, like me, may be looking for the plain English version of some of these topics that get thrown around in search conversations. "Reindexing" is one of those topics that's a little more complex to understand, mostly because it covers so many different situations.

Consider this the non-engineer's guide to reindexing. Here's what it is, why it happens more than you'd expect, and why you may want someone else doing it for you.

### What is an "index?"

![An index in the back of a book](https://bonsai.io/blog/why-is-reindexing-so-important/image_0.png)

At its most basic level, you already know what an index is. A cookbook has one: flip to the back, look up "chicken," and it tells you exactly which pages to check without reading the whole book.

Search engines build the same kind of thing. It's a list of words and where to find them, so a search doesn't have to scan every single item to find a match. The word "index" also does double duty in search engines. "Index" is also the name for a container that holds the things that people need to find.

Easy enough.

That part is straightforward. It gets more complex when you ask who decides what belongs in the index. A book's index is built by a person who reads it and decides what's worth including. "Chicken" made the cut because someone decided it mattered. A search engine doesn't have a person doing that for every product or article as it comes in. It has to decide algorithmically, and quickly, what counts as a match, what's worth weighting, and what to ignore. Building that well is the real work of a useful index, and it's what decides whether results actually reflect what your customers mean.

If you want the fuller illustrated walkthrough of how an index actually gets built, we've got one at [storyofsearch.com](http://storyofsearch.com/). There's even an interactive example for you hands-on learners.

### **So what does it mean to "re-index?"**

When an index is first built, the rules for what counts as a match and the container that organizes your content are locked in. Neither can be edited in place. The cookbook analogy holds here too. Once it's printed, that index is set in every copy. If you need to add a new category, drop "broccoli" entirely, or reorganize the whole thing, you can't just swap out one page. You have to print it again.

Search indexes work the same way. Change any part of it, and the whole thing has to be rebuilt from scratch under the new rules, the same way a cookbook gets reprinted. That full rebuild is reindexing.

The difference is that a cookbook might get a reprinted edition every few years, if that. A search index changes far more often. What counts as a good match keeps shifting. Your catalog of products changes, your customers' language changes, and you learn more every day from what people actually search for, click on, and give up on. For a business running search against millions of records, this happens again and again, driven by real signals about how customers search rather than any fixed schedule.

* * *

![Looking up an index value in a database](https://bonsai.io/blog/why-is-reindexing-so-important/image_1.png)

### **When and why do you re-index?**

In our experience, it almost always comes down to one of these:

1.  **Make search more relevant.** The relevancy of your results isn't fixed. As you learn more about what your customers actually search for, you'll want to change how results are ranked, and that means rebuilding the index. More on this below, since it's the part that matters most for relevance and AI.
2.  **Change what search can find.** Businesses change what they sell and how they describe it. Adding a field your team now depends on, or dropping one you don't need (an old product code), means rebuilding around the new structure.
3.  **Right size the infrastructure underneath.** The number of pieces your data is split into is locked in when the index is created, so as your business grows and needs more or different servers, redistributing data evenly means [rebuilding the index around a new split](https://bonsai.io/blog/why-is-reindexing-so-important/@blog/why-your-cluster-composition-matters/). Get this wrong and you're either paying for capacity you don't need, or search slows down and risks going down altogether.
4.  **Turn on cost saving settings after the fact.** Some cost-saving settings, like data compression, only affect data indexed after you turn them on, not what's already there. Switch one on today, and older records stay uncompressed until you rebuild, meaning you're paying to store air. Rebuilding applies compression retroactively, which can shrink storage by roughly 30 percent for the same data.
5.  **General housekeeping.** Record updates, like a price change, usually write a new copy instead of editing in place, and the old one doesn't always get cleaned up right away. We've seen customers where that adds up to 20 to 50 percent of their storage being dead weight, the equivalent of paying full rent on a storage unit that's only half full of stuff you meant to donate three years ago. Reindexing clears it out.

![The database to search indexing process](https://bonsai.io/blog/why-is-reindexing-so-important/image_2.png)

### **Why this matters even more for AI-powered search**

If you run search for your site, or you are a product leader, you're being asked about AI. Your leadership [wants a roadmap](https://bonsai.io/blog/why-is-reindexing-so-important/@blog/surviving-the-ai-mandate/), your customers expect a smarter search bar, and your competitor has already shipped something "AI powered" that's pulling your customers away. That pressure is real, and it isn't going away.

Ship natural language search, [semantic matching](https://bonsai.io/blog/why-is-reindexing-so-important/@blog/when-to-use-vector-search/), or a chatbot that pulls answers from your own content, and you run into the same problem described above. Adding those capabilities usually means storing new kinds of data, like vector embeddings, alongside what you already have, which means rebuilding the index around a new structure.

Relevance works the same way. How well your search understands customers has to keep changing as your catalog grows and as people describe things differently than you expected.

Being able to reindex quickly and safely is what actually lets you ship on that AI roadmap.

### **How Bonsai can help**

Any capable engineering team can technically kick off a reindex job. [Doing it safely and well is the harder part](https://bonsai.io/blog/why-is-reindexing-so-important/@blog/risky-operations-in-elasticsearch-and-opensearch/), and teams get understandably stuck there.

The configuration is finicky. Deciding which rules to change, and in what order, without breaking search for half your catalog, takes real expertise. Our relevance work lives here. We help you decide what's worth changing before anyone touches the technical job.

Getting it wrong takes production down. [Reindexing can be a risky operation in Elasticsearch and OpenSearch](https://bonsai.io/blog/why-is-reindexing-so-important/@blog/risky-operations-in-elasticsearch-and-opensearch/). If you reindex directly against live traffic, the job competes with real customers for resources, taking search down while it runs, usually during a traffic spike, which is exactly when your customers need it to work. That's an outage that's entirely avoidable, and we all know there is nothing worse than that.

The safe way requires infrastructure most teams don't have sitting around. The right approach is to build the new index somewhere else entirely, on infrastructure spun up specifically for that job, and only cut over once it's ready, so production is never at risk. That means provisioning and tearing down infrastructure on demand, and most teams either can't do that quickly or would rather not spend engineering time building that muscle.

We bring both halves: the expertise to know what actually improves relevance and AI readiness, and the infrastructure to make changes without risking your live search. Put those two together, and reindexing stops being a fire drill. It becomes routine background work while your search keeps getting better.

Ready to have an actual answer the next time someone asks what your AI plan is? [Contact us](https://bonsai.io/contact)

_Copyright ©️ Bonsai.io, 2026 · By Elyse Munselle · Originally published at https://bonsai.io/blog/why-is-reindexing-so-important/ · CC BY-SA 4.0_