Pierre Zemb

jakelazaroff.com Just a programmer trying to make a home for myself on the WWW.

An Interactive Intro to CRDTs | jakelazaroff.com jakelazaroff.com/words/an-int...

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.

📝 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

TLA+ By Example tlabyexample.com

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.

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!)

committers.top - Most active GitHub users in France A list of most active GitHub users in France.

👀 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

Simulating Leader Election on top of FoundationDB Can LLM-generated code be trusted for distributed systems? Only if you have the right feedback loop.

✍️ 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

FoundationDB's Transaction Model for Layer Engineers How optimistic concurrency control works in FoundationDB, and how to design data structures that stop fighting it

💡 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...

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 🥵

Right. To me, it truly feels like iterating and chatting with someone other a committed file. Like a colleague, or the good old rubber duck debugging

I haven’t tried Kiro yet. What’s your opinion about it?

GitHub - github/spec-kit: 💫 Toolkit to help you get started with Spec-Driven Development 💫 Toolkit to help you get started with Spec-Driven Development - github/spec-kit

Have you tried github.com/github/spec-...?
It is pretty useful to get the sense of spec-driven development?

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.

✍️ 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

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...

RUST REFLECTION MVP HAS LANDED https://github.com/rust-lang/rust/pull/146923

THIS IS NOT A DRILL

my coworker finch: rain (they/she): another victory for RFD 619 as LLM guide: i got claude to rebase my TQ sled-agent API additions across the changeover to RFD 619 versioning by feeding it the full RFD and asking it to fix merge conflicts and refactor for conformity with the RFD. Worked like a charm, very little user direction needed other than accepting changes. has 3 fire emoji reactions

cool benefit of machine-executable specs -- they can be used by everyone, not just the author

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.

🎄 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...

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.

🔧 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-...

What Does a Database for SSDs Look Like? - Marc's Blog brooker.co.za/blog/2025/12...

Designing Rust FDB Workloads That Actually Find Bugs Patterns and principles for writing Rust simulation workloads that catch bugs before production does.

🧪 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...

Grown-up ZFS Data Corruption Bug Épisode de l’émission · Oxide and Friends · 26/11/2025 · 1 h 21 min

This is an awesome podcast episode about debugging a Grown-up #ZFS Data Corruption Bug podcasts.apple.com/fr/podcast/o...

Currently having a lot of fun modeling some internal spec in #fizzbee!

How to (badly) start a week #squash

Oooooh, I didn’t know Fizzbee! Will give it a try, thanks a lot for sharing.

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...

Merci ☺️

DataFusion 51.0.0 release blog: datafusion.apache.org/blog/2025/11...

Oxide and Friends 11/24/2025 -- A Grown-up ZFS Data Corruption Bug YouTube video by Oxide Computer Company

Hey hey! We recently tripped over a ZFS data corruption bug–introduced over 18 years ago! @bcantrill.bsky.social and I discuss with members of the Oxide team as well as Matt Ahrens, the co-inventor of ZFS.

New books to finish the year!

An evolution of xkcd #2347 with too many things that can break the Internet!

This meme is getting out of hand, but it's actually not far from reality 🤣

A 'small' vanilla Kubernetes install on NixOS stephank.nl/p/2025-11-17...

Stéphane Nicoll nous parle de Spring 4.

Stéphane Nicoll nous parle de Spring 4.

D'autres meetups ont des soucis de no-show, nous on a la chance d'avoir de l'over-show ! 26 inscrits, 37 présents pour le super talk de @snicoll.be sur #spring 4.

Parce que oui, nous somme toujours un JUG, FinistJUG forever ☕️ #java #spring

Merci encore à #Zenika #Brest pour l'accueil !