Ask HN: How can I load test PostgreSQL but avoid changing actual data?

1•LawZiL•9mo ago

I'm running a load test on my Node.js application and want to simulate realistic write-heavy scenarios to stress test the system — especially the PostgreSQL database.

There's a part of the code that performs UPDATE queries, but during load testing, I don't want these updates to actually change the state of the database. However, I still want the database to experience the full impact of the update — query planning, locking, I/O, WAL writes, etc. — so I can measure how it affects performance under peak load.

Is there a best-practice approach to achieve this?

So far, the most viable option I’ve found is to wrap the UPDATE queries in a transaction and then roll it back — that way, the queries still execute, but the state doesn’t change. Is this the right way to go? Does rollback introduce any performance overhead that would skew my results? Are there better or more realistic alternatives that simulate the full write path without persisting changes?

Thanks in advance!

Comments

sargstuff•9mo ago

pgbench[2] / pgreplay-go[0] / python locust[1]

very old school approach:

Misuse sql VIEW[3][4] to generate a temporary parallel table setup. Testing database separate from production database would be 'better', IMHO.

-----

[0] pgreplay-go : https://github.com/gocardless/pgreplay-go

[1] python locust : https://miguel-codes.medium.com/unconventional-load-testing-...

[2] pgbench load testing :

   a) https://medium.com/@c.ucanefe/pgbench-load-test-166bdfb5c75a

   b) https://neon.tech/blog/autoscaling-in-action-postgres-load-testing-with-pgbench

   c) https://hackernoon.com/how-to-create-and-load-test-data-in-postgresql-i41e353m

----------------------------

[3] : a) https://hashrocket.com/blog/posts/materialized-view-strategi...

      b) https://tech.jonathangardner.net/wiki/PostgreSQL/Materialized_Views

      c) https://stackoverflow.com/questions/77603705/what-is-the-use-of-materialized-view-in-postgresql

[4] : https://en.wikipedia.org/wiki/View_(SQL)

LawZiL•9mo ago

but again, how can i perform the query, but not actually change the state, i really need the state to keep untouched, but be able to perform the query itself.

MatthiasPortzel•9mo ago

> Does rollback introduce any performance overhead that would skew my results?

I would expect it to be the other way around—since the transactions are rolled back and not committed, they would have significantly less performance impact. But I’m working from an academic model of the database.

apothegm•9mo ago

Load test against a clone instead of a DB whose contents you care about?

Cistercian Numbers

Nchat – WhatsApp via Terminal

Qwen3.5-397B-A17B-FP8 weights are now available

Web 4.0

What I learned analyzing 1k AI agent turns: Sessions are trajectories

Jury told that Meta, Google 'engineered addiction' at landmark US trial

Glowing bacterial sensors detect gut illness in mice before symptoms emerge

Show HN: Trust Protocols for Anthropic/OpenAI/Gemini

Taming Claude Code: Taking Back Control

86% of Americans want Meta, Google held accountable for 'predatory' social media

Climber on trial for leaving girlfriend to die on Austria's highest mountain

Show HN: AFS – filesystem-native memory layer for AI agents

Show HN: allsee – fast cross-platform file search built with Rust and Tauri

A 5-20x faster experimental Homebrew alternative

Software as Wiki, Mutable Software

"AI Agent Standards Initiative" for Interoperable and Secure Innovation

Unity CEO says an upcoming Beta will allow to "prompt full casual games"

Finding a non-square mod p

Finding a square root of -1 mod p

Wagon's Algorithm in Python

Show HN: Mailpeek – Vue.js email preview component (Gmail/Outlook rendering)

Google's Lyria 3 AI music model is coming to Gemini today

Show HN: AgentDX – Open-source linter and LLM benchmark for MCP servers

Zero-day CSS: CVE-2026-2441 exists in the wild

The Scarcity Trap: Why AI Still Feels Like a Metered Utility

Show HN: A Unix environment in a single HTML file (420 KB)

Show HN: Sher – Instant Preview Environments

Becoming a Research Engineer at a Big LLM Lab: 18 Months of Strategic Career Dev

Token_ledger – Ruby gem for auditable token accounting in Rails

Heaper: Local-first PKM for all filetypes with multi-device sync, tags and links