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Pierre Zemb

@pierrezemb.fr
898 followers 661 following 244 posts

🧑‍💻 Staff Engineer @clever-cloud.com 🤩 Distributed and Database Systems 🚀 Co-leader Finistdevs.org 💪 Squash player

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Pierre Zemb @pierrezemb.fr · 13h
Seeing Claude Code web debugging it’s own MR through deterministic simulation is always a joy
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Clever Cloud @clever.cloud · 22/09/2026
[𝗘𝗩𝗘𝗡𝗧] Deux jours, deux talks et l’équipe Clever à Clermont-Ferrand : direction @volcampio.bsky.social ! 🌋 @pierrezemb.fr & Alexandre Burgoni parleront d’ETCD et Kubernetes, @lostinbrittany.bsky.social d’architecture cloud. 📍 1 & 2/10 www.billetweb.fr/volcamp-2026 🧵👇 Thread
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Pierre Zemb @pierrezemb.fr · 22/09/2026
Jev introduces a new shape of LLM—System One, aka Decision Models simonwillison.net/2026/Sep/21/...
simonwillison.net
Jev introduces a new shape of LLM—System One, aka Decision Models
Last week TypeSafe AI unveiled Jev, their first example of a new category of model that they are calling “System One models” (I’m with Maggie Appleton, I think “decision models” …
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Pierre Zemb @pierrezemb.fr · 21/09/2026
The architecture of Neki — PlanetScale planetscale.com/blog/the-arc...
planetscale.com
The architecture of Neki — PlanetScale
Sharded Postgres, from the team behind Vitess
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Pierre Zemb @pierrezemb.fr · 15/09/2026
Any Nix package, live in your browser fzakaria.com/2026/09/04/a...
fzakaria.com
Any Nix package, live in your browser
tl;dr Try it at https://trynix.dev. Click hello, or python 3.6.2 from 2017, or two eras of hello at once, or a package that exists in no public cache. A Linux machine boots in the tab and you get a…
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Pierre Zemb @pierrezemb.fr · 28/08/2026
For the past two years, I’ve been building my own deterministic simulation framework in rust, and now I’m having fun learning Paxos with DST as the harness. 2026 is wild for engineers 😎
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Pierre Zemb @pierrezemb.fr · 14/08/2026
I just published a new blogpost about one of my favorite papers I discovered this year: "Explaining #FoundationDB's Architecture Through Compartmentalization" pierrezemb.fr/posts/founda...
pierrezemb.fr
Explaining FoundationDB's Architecture Through Compartmentalization
Compartmentalization explains FoundationDB's architecture: find the responsibilities that got coupled together, split them, and scale only the parts that can scale.
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Pierre Zemb @pierrezemb.fr · 11/08/2026
NVMe Polishes Its Specs, Brings Virtualization to Locally Attached SSDs - Slashdot hardware.slashdot.org/story/26/08/...
hardware.slashdot.org
NVMe Polishes Its Specs, Brings Virtualization to Locally Attached SSDs - Slashdot
The latest NVMe specifications add SSD-level virtualization that can simplify live VM migration by preserving storage identities across servers. The updates also introduce support for post-quantum…
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Pierre Zemb @pierrezemb.fr · 30/07/2026
#ApacheAvro frustrates a lot of people: you need two schemas just to decode a record. That annoyance is exactly why I like it. Here's why schema resolution makes rolling upgrades boring, in a good way. pierrezemb.fr/posts/why-ap...
pierrezemb.fr
Why Apache Avro Needs Two Schemas
Avro payloads cannot be decoded without the writer schema, and that two-schema model is what makes rolling upgrades and schema evolution work.
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Martin Kleppmann @martin.kleppmann.com · 26/07/2026
Engineering management after the cost of code collapsed: “Investing in machine-checkable correctness is now among the highest-leverage infrastructure work an org can fund” karimjedda.com/engineering-...
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Sunny Tech @sunnytech.bsky.social · 02/07/2026
☀ "Et si on faisait du simulation-driven development ?" par @pierrezemb.fr Découvrez le Deterministic Simulation Testing (DST) pour simuler et diagnostiquer les scénarios et pannes de systèmes complexes de manière totalement déterministe. #SunnyTech
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Clever Cloud @clever.cloud · 22/06/2026
📍 @sunnytech.bsky.social — 02 & 03/07, Montpellier Retrouvez Julia Buchner, Pierre Zemb, @LostInBrittany, Alexandre Burgoni et Aurélien Hébert sur notre stand. @pierrezemb.fr y donnera aussi sa conférence : « Et si on faisait du simulation-driven development ? ». sunny-tech.io
sunny-tech.io
Sunny Tech
Sunny Tech est la 1ère conférence Tech organisée à Montpellier. Une conférence annuelle des technologies du numérique, créée par des passionnés, pour des passionnés avec l’ambition de rayonner nationa...
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Pierre Zemb @pierrezemb.fr · 18/06/2026
Honored to be featured by @eatonphil.bsky.social in The Consensus 🙏 We talked about the data services we are building at @clever.cloud, all API-compatible with Redis, PostgreSQL and etcd on top of FoundationDB. Give it a read 👇
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Phil Eaton @eatonphil.bsky.social · 18/06/2026
I spoke with Pierre Zemb from French neo-compute company Clever Cloud. They're building data services API-compatible with popular systems like Redis, PostgreSQL, and etcd on top of FoundationDB and Pierre is leading the work. There is no paywall, give it a read. theconsensus.dev/p/2026/06/18...
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Pierre Zemb @pierrezemb.fr · 11/06/2026
Me, denied by FoundationDB's simulation because my PoC wasn't reboot-proof 🤯
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Pierre Zemb @pierrezemb.fr · 09/06/2026
I just published 'Designing Fakes That Prove Correctness' ✍️ The blog also has a new theme, and it hides a quorum easter-egg: flip to single-replica reads and see what it was protecting you from 👀 pierrezemb.fr/posts/design...
pierrezemb.fr
Designing Fakes That Prove Correctness
You fake the handful of methods your code actually calls, prove the fake stays honest, and then make it fail the way production does.
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Pierre Zemb @pierrezemb.fr · 27/05/2026
Building an AsyncIO executor for the 3DS blog.cat-girl.gay/3ds-async-pa...
blog.cat-girl.gay
Building an AsyncIO executor for the 3DS (pt 1!)
the Nintendo 3DS is a very fun device to write homebrew for, but one thing about it can be annoying: its multitasking is non-preemptive! in this little se...
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Clever Cloud @clever.cloud · 13/05/2026
[𝗖𝗞𝗘] Quand @zwindler.fr attend notre Kubernetes managé depuis des années, puis ouvre le capot dès la bêta publique, forcément on lit attentivement 👀 Merci Denis pour ce retour et vivement la partie 2 !
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FinistDevs @finistdevs.bsky.social · 06/05/2026
La session de mai du FinistDevs, c’est mardi 12 mai à 18h30 chez Zenika Brest. Au programme • Xavier Rollet: “Un environnement de dev sur mesure avec NixOS” • Benoît Morin / Ifremer: “Centre Datarmor”, HPC, IA, big data et infrastructures scientifiques Inscription : www.meetup.com/finistdevs/e...
meetup.com
Soirée FinistDevs Mai 2026, Tue, May 12, 2026, 6:30 PM | Meetup
Salut à toutes et à tous, La session de mai du FinistDevs aura lieu le **mardi 12 mai à 18h30**, toujours chez **Zenika Brest**. Au programme : deux talks, avec du Linux
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Pierre Zemb @pierrezemb.fr · 05/05/2026
I gave a lightning talk at #BugBash 2026, sharing the stage with people whose work shaped how I think about distributed systems. Still processing that. Wrote up why the correctness decade has started, and why you trust the simulator, not Claude 👀 pierrezemb.fr/posts/bugbas...
pierrezemb.fr
BugBash 2026, or how the correctness decade has started
A retrospective on BugBash 2026, and why software engineering looks brighter than ever.
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Sylvain Wallez @swallez.com · 21/04/2026
Et hop, je mets la touche finale à mes slides alors que le train arrive à Montparnasse. C'est bon, je suis prêt pour @devoxx.fr demain matin ! Si vous voulez savoir comment marche un moteur de requête, c'est demain à 10h30 ! m.devoxx.com/events/devox...
m.devoxx.com
Devoxx Mobile Companion
Your ultimate companion for Devoxx conferences worldwide. Browse talks, speakers, schedules, and manage your personalized conference experience.
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Pierre Zemb @pierrezemb.fr · 20/04/2026
On my way to #BugBash 2026 🤩 First Paris, then Washington DC ✈️ I will be presenting a lightning talk about how we borrowed #foundationdb simulation framework in #rustlang
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Phil Eaton @eatonphil.bsky.social · 09/04/2026
DataFusion 53 came out last week. I took a look at the individuals and companies who committed the most. (paywall has expired) theconsensus.dev/p/2026/04/03...
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Pierre Zemb @pierrezemb.fr · 09/04/2026
How #NASA Built #Artemis II’s Fault-Tolerant Computer – Communications of the ACM cacm.acm.org/news/how-nas...
cacm.acm.org
How NASA Built Artemis II’s Fault-Tolerant Computer – Communications of the ACM
Membership in ACM includes a subscription to Communications of the ACM (CACM), the computing industry's most trusted source for staying connected to the world of advanced computing.
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Pierre Zemb @pierrezemb.fr · 26/03/2026
I just published a post on why I think fakes are more powerful than both mocks and Testcontainers. A fake that is worse than production: dropping writes, returning stale data... It catches the bugs that containers faithfully hide. pierrezemb.fr/posts/why-fa...
pierrezemb.fr
Why Fakes Beat Mocks and Testcontainers
Trait-based fakes test partial failures that mocks and Testcontainers fundamentally cannot simulate. They are also the on-ramp to simulation-driven development.
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Pierre Zemb @pierrezemb.fr · 25/03/2026
I just gave a talk "Testing: prevention vs discovery" at the #FinistAI x #FinistDevs crossover meetup 🧪 DST is the ultimate feedback loop for LLMs. It lets them discover what they don't know. No recording, but slides are available: pierrezemb.fr/slides/2026-... #deterministic #simulation #LLMs
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Pierre Zemb @pierrezemb.fr · 23/03/2026
👀 How does a #fuzzer find a 3-byte crash sequence in 9,000 iterations instead of 16 million? 🛠 Coverage turns a multiplicative problem into an additive one. I built a minimal #rustlang fuzzer from scratch to understand how it works: pierrezemb.fr/posts/diving...
pierrezemb.fr
Diving Into Coverage-Guided Fuzzing
How a 600-line Rust fuzzer discovers a 3-byte crash sequence in 9,000 iterations instead of 16 million
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Pierre Zemb @pierrezemb.fr · 20/03/2026
🎉 I will be speaking at #SunnyTech 2026 about simulation-driven development! #SeaTechAndSun
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Pierre Zemb @pierrezemb.fr · 18/03/2026
Rob Pike's 5 Rules of Programming "write stupid code that uses smart objects" is my favorite one! www.cs.unc.edu/~stotts/COMP...
cs.unc.edu
Rob Pike's 5 Rules of Programming
Pike's rules 1 and 2 restate Tony Hoare's famous maxim "Premature optimization is the root of all evil."
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Pierre Zemb @pierrezemb.fr · 18/03/2026
Google Engineers Launch "Sashiko" For Agentic AI Code Review Of The Linux Kernel - Phoronix www.phoronix.com/news/Sashiko...
phoronix.com
Google Engineers Launch "Sashiko" For Agentic AI Code Review Of The Linux Kernel
Google engineers have been spending the past number of months developing Sashiko as an agentic AI code review system for the Linux kernel
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Pierre Zemb @pierrezemb.fr · 17/03/2026
"Even in healthy clusters, MariaDB Galera Cluster exhibited Lost Update and Stale Read" Jepsen: MariaDB Galera Cluster 12.1.2 jepsen.io/analyses/mar...
jepsen.io
Jepsen: MariaDB Galera Cluster 12.1.2
MariaDB Galera Cluster is a replicated version of MariaDB, a popular SQL database. While MariaDB claims Galera ensures “no lost transactions”, it loses transactions in at least two scenarios. First,…
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Pierre Zemb @pierrezemb.fr · 05/03/2026
An Interactive Intro to CRDTs | jakelazaroff.com jakelazaroff.com/words/an-int...
jakelazaroff.com
jakelazaroff.com
Just a programmer trying to make a home for myself on the WWW.
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Pierre Zemb @pierrezemb.fr · 25/02/2026
📝 The datafusion-index-provider PoC from last year is now a real library in datafusion-contrib, running in production. 🔧 New post on building secondary index queries with standard DataFusion operators pierrezemb.fr/posts/datafu... #Rust #DataFusion
pierrezemb.fr
Building Index-Backed Query Plans in DataFusion
What I learned about manually constructing physical query plans for secondary index queries, and the library that came out of it.
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Pierre Zemb @pierrezemb.fr · 24/02/2026
TLA+ By Example tlabyexample.com
tlabyexample.com
TLA+ By Example
Learn TLA+ specifications through interactive examples in your browser
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Martin Kleppmann @martin.kleppmann.com · 18/02/2026
The second edition of Designing Data-Intensive Applications, by myself and @chris.blue, is finished and sent off to the printers! Ebooks should be available in the next week, and print books in 3–4 weeks. Sigh of relief. 😅 (BTW, this is a good opportunity to support your favourite local bookshop!)
Book cover of "Designing Data-Intensive Applications, 2nd edition". It has a similar wild boar on the cover as the first edition, but it uses O'Reilly's new cover design, and the boar is now slightly colourised.
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Pierre Zemb @pierrezemb.fr · 14/02/2026
👀 Turns out I'm #163 on the most active GitHub committers list in France A non-trivial amount of credit goes to #ClaudeCode, my favorite coding partner these days! committers.top/france
committers.top
committers.top - Most active GitHub users in France
A list of most active GitHub users in France.
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Pierre Zemb @pierrezemb.fr · 05/02/2026
✍️ I just published "Simulating Leader Election on top of FoundationDB" 🧪 Can LLM-generated code be trusted for distributed systems? Only if you have the right feedback loop. pierrezemb.fr/posts/simula... #FoundationDB #rustlang #simulation
pierrezemb.fr
Simulating Leader Election on top of FoundationDB
Can LLM-generated code be trusted for distributed systems? Only if you have the right feedback loop.
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Pierre Zemb @pierrezemb.fr · 30/01/2026
💡 In #FoundationDB, your reads determine whether YOU conflict. Your writes determine what OTHERS conflict with. ✍️ Wrote about OCC patterns for layer engineers: phantom conflicts, snapshot reads, atomic ops, and versionstamps. pierrezemb.fr/posts/fdb-tr...
pierrezemb.fr
FoundationDB's Transaction Model for Layer Engineers
How optimistic concurrency control works in FoundationDB, and how to design data structures that stop fighting it
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Pierre Zemb @pierrezemb.fr · 17/01/2026
I recently had an intense #squash match this morning, lasting an hour and ending with a 3-2 victory ✌️ Throughout the entire game, I maintained a heart rate consistently above 190 beats per minute 🥵
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Pierre Zemb @pierrezemb.fr · 15/01/2026
✍️ I keep having the same conversation with colleagues about using LLMs for code. Finally wrote it down. Planning, context, feedback loops, and why simulation + LLMs is a powerful combo. pierrezemb.fr/posts/llms-f... #llm #rustlang #testing
pierrezemb.fr
What I Tell Colleagues About Using LLMs for Engineering
LLMs amplify expertise, they don't replace it. Here's what works: planning, context, feedback loops, and building systems that let AI discover bugs.
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Reposted by Pierre Zemb
amos @fasterthanlime.hachyderm.io.ap.brid.gy · 10/01/2026
RUST REFLECTION MVP HAS LANDED github.com/rust-lang/rust/pull/1469… THIS IS NOT A DRILL
github.com
Reflection MVP by oli-obk · Pull Request #146923 · rust-lang/rust
I am opening this PR for discussion about the general design we should start out with, as there are various options (that are not too hard to transition between each other, so we should totally jus...
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Pierre Zemb @pierrezemb.fr · 26/12/2025
🎄 Before heading to holidays, I wrote my 2025 year in review. ✍️ Back to engineering after 2 years of management. Built moonpool, a #FoundationDB simulation framework in #rustlang. Published 20 posts. Learned to work with LLMs. A year of going deeper. pierrezemb.fr/posts/2025-y...
pierrezemb.fr
2025: A Year in Review
Reflections on returning to engineering, discovering simulation as a superpower, learning to work with LLMs, and the compounding value of years of distributed systems work.
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Pierre Zemb @pierrezemb.fr · 19/12/2025
🔧 I just published a blogpost about specs in the #LLM era. Model checkers like #Fizzbee work for algorithms. But for APIs and business logic? The tooling doesn't exist yet. pierrezemb.fr/posts/specs-...
pierrezemb.fr
Specs Are Back, But We're Missing the Tools
LLMs revived specifications. Model checkers like Fizzbee work for algorithms. But for APIs and business logic? The tooling doesn't exist yet.
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Pierre Zemb @pierrezemb.fr · 16/12/2025
What Does a Database for SSDs Look Like? - Marc's Blog brooker.co.za/blog/2025/12...
brooker.co.za
What Does a Database for SSDs Look Like? - Marc's Blog
Maybe not what you think.
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Pierre Zemb @pierrezemb.fr · 09/12/2025
🧪 How do you test #rustlang code that runs on top of #FoundationDB? ✍️ I wrote about designing simulation workloads: the patterns that find real bugs, the rules you can't break, and the pitfalls pierrezemb.fr/posts/writin...
pierrezemb.fr
Designing Rust FDB Workloads That Actually Find Bugs
Patterns and principles for writing Rust simulation workloads that catch bugs before production does.
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Pierre Zemb @pierrezemb.fr · 06/12/2025
This is an awesome podcast episode about debugging a Grown-up #ZFS Data Corruption Bug podcasts.apple.com/fr/podcast/o...
podcasts.apple.com
Grown-up ZFS Data Corruption Bug
Épisode de l’émission · Oxide and Friends · 26/11/2025 · 1 h 21 min
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Pierre Zemb @pierrezemb.fr · 04/12/2025
Currently having a lot of fun modeling some internal spec in #fizzbee!
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Pierre Zemb @pierrezemb.fr · 01/12/2025
How to (badly) start a week #squash
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Pierre Zemb @pierrezemb.fr · 28/11/2025
I think I finally have a problem where I'd genuinely feel safer writing a TLA+ spec before even touching simulation code. Time to actually learn it. #tlaplus lamport.azurewebsites.net/video/videos...
lamport.azurewebsites.net
TLA+ Video Course
A Word of Warning These videos are not light entertainment. They require careful viewing and actual thinking. You may often stop a video to digest what you've just seen, and perhaps to skip back and…
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