![Why are some people more boring while others are less boring [closed]](https://cdn.sstatic.net/Sites/interpersonal/Img/apple-touch-icon@2.png?v=17e836faa592)
_Vladimir_Stanisic_Alamy.jpg?width=1280&auto=webp&quality=80&disable=upscale#)
#Elasticsearch #
Elasticsearch is powerful, but when you're running updates on a large index, you might suddenly notice something scary: your cluster slows down, gets stuck, or even blocks entirely. If you've hit this frustrating wall — don't worry. Let's break down why it happens, what’s going on under the hood, and how to fix or avoid it. ❓ What's Really Happening? When you update a document in Elasticsearch, it doesn't update it in place. Instead, Elasticsearch: Marks the old document as deleted, Indexes a new version of the document. This means updates are effectively new writes plus old deletions. In small indexes, this isn't a problem. But in huge indexes (millions+ documents): Massive delete markers pile up. Segment files get bloated. Disk I/O becomes heavy. Cluster memory pressure rises. Eventually, Elasticsearch pauses indexing or blocks updates to protect cluster health. You might see errors like: cluster_block_exception or flood_stage disk watermark exceeded
Elasticsearch is powerful, but when you're running updates on a large index, you might suddenly notice something scary: your cluster slows down, gets stuck, or even blocks entirely.
If you've hit this frustrating wall — don't worry. Let's break down why it happens, what’s going on under the hood, and how to fix or avoid it.
❓ What's Really Happening?
When you update a document in Elasticsearch, it doesn't update it in place. Instead, Elasticsearch:
- Marks the old document as deleted,
- Indexes a new version of the document.
This means updates are effectively new writes plus old deletions.
In small indexes, this isn't a problem.
But in huge indexes (millions+ documents):
- Massive delete markers pile up.
- Segment files get bloated.
- Disk I/O becomes heavy.
- Cluster memory pressure rises.
Eventually, Elasticsearch pauses indexing or blocks updates to protect cluster health.
You might see errors like:
cluster_block_exception
or
flood_stage disk watermark exceeded
![[Boost]](https://media2.dev.to/dynamic/image/width=800%2Cheight=%2Cfit=scale-down%2Cgravity=auto%2Cformat=auto/https%3A%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F1065945%2Fa6eebe7a-08cf-440b-8b71-8c5b01256e1f.png)
