---
title: "Discussion on \"PostgreSQL JSONB Write Amplification: TOAST Chunk Fragmentation and Unseen I/O Thrashing\" | Hashnode"
description: "Discussion on \"PostgreSQL JSONB Write Amplification: TOAST Chunk Fragmentation and Unseen I/O Thrashing\". Why a one-key jsonb_set() rewrites the whole document, and how to stop JSONB from flooding your WAL"
url: "https://hashnode.com/posts/postgresql-jsonb-write-amplification-toast-fragmentation/6ace56ba75b77f8151648cd5"
---

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# [PostgreSQL JSONB Write Amplification: TOAST Chunk Fragmentation and Unseen I/O Thrashing](https://ctousman.hashnode.dev/postgresql-jsonb-write-amplification-toast-fragmentation?utm_source=hashnode&utm_medium=feed)

Why a one-key jsonb\_set() rewrites the whole document, and how to stop JSONB from flooding your WAL

Oct 13 · 6 min read · ctousman.hashnode.dev  
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## Written by

[Usman Khan](https://hashnode.com/@usmankhan-io)

@usmankhan-io · Karachi, Pakistan

  
[View profile](https://hashnode.com/@usmankhan-io)

Fractional CTO & Founder at Zentiq Labs | B2B SaaS Architecture, Distributed Systems & AI Integration | ctousman.com

Usman Khan is a Fractional CTO, Lead Systems Architect, and Founder of Zentiq Labs. With over 13 years of experience engineering high-concurrency B2B SaaS applications, he specializes in multi-tenant database isolation (PostgreSQL RLS), distributed Redis caching patterns, and production AI/LLM integrations. Usman writes architectural deep dives and engineering guides at ctousman.com.

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