Nikos Karayannidis

I am pleased to announce the release of a new #Haskell #ETL Library, namely DBFunctor-0.1.0.0. For more information please check out the project homepage: github.com/nkarag/haskell…

AI is writing a growing share of the world's software. No one is formally verifying any of it. New essay: "When AI Writes the World's Software, Who Verifies It?" leodemoura.github.io/blog/2026/02/2…

excerpt from a longer paper Ensuring safety for powerful learned systems requires a fundamentally different foundation based on mathematically provable constraints on the acts an AI may perform. Such a foundation must rest on a simple principle: we should never trust an AI’s outputs or intentions by default, no matter how competent or aligned it appears; trust must be earned only through verifiable, enforceable proofs of safety for each act. Our assumption that enacting unsafe AI acts is worse than rejecting safe AI acts leads to the central premise of our work, the Universal Declaration of AI Acts: No AI act may be treated as safe unless harmlessness is proven mathematically. Note that this is the mathematical dual of the Universal Declaration of Human Rights: No person may be treated as guilty unless guilt is proven, which is based on the assumption that punishing an innocent person is worse than letting a guilty person go.

@catalinmpit Reduce your sleep hours and work very early in the morning or late at night, or both. In any case you are going to suffer so you must be really determined. Don’t do this everyday to retain some balance.

It's crazily difficult to build things on the side with a full-time job and a baby. I'm extremely grateful for both, especially for my family. They're the reason why I'm doing all of this and the only ones truly important. But I need to find a system that allows me to do all of them. For people in the same situation, how do you do it?

You don’t hate math. You hate the way it was taught to you. But because you haven’t learned math properly, you confuse correlation and causation, and therefore think that you hate math.

"Mathematics for Computer Science" from MIT. This complete book of 1048 pages is now FREE.

Nice blogpost by @muratdemirbas on the foundational treatment of serializability theory in databases from Chapter 2 of the book Concurrency Control and Recovery in Database Systems (1987) by Bernstein, Hadzilacos, and Goodman. I started reading the post and after a bit of exploration found this foundational 1979 paper on Serializability of Concurrent Database Updates by Christos H Papadimitriou. This paper has been referenced in Bernstein's book as well. Looks like Papadimitriou has also written quite a lot on the theory of database concurrency control .. Looking forward to some weekend readings .. links to blog post and the paper: 👇

🏆 The ACM SIGMOD Test of time award (2025) goes to K-shape: Efficient and accurate clustering of time series John Paparrizos, Luis Gravano 2025.sigmod.org/sigmod_awards.…

New blog post on the mental model I've used when working through complex or confusing papers on transactional systems. transactional.blog/blog/2025-deco…

This paper covering the internals and architecture of @ClickHouseDB is one of the best in database architecture that I read in 2024. Some great insights on SIMD and Multicore parallelisation of the query processing layer, query compilation based on LLVM, the various data structures for aggregation and hash joins, data pruning techniques in the storage layer and lots and lots of information related to the architecture. Loved it ..

The first two videos for @CMUDB's latest seminar series on Database Building Blocks are now posted. You should start off with @andrewlamb1111's fantastic introductory overview to @ApacheDataFusio: youtube.com/watch?v=iJhRbD…

Elizabeth Garrett Christensen (@sqlliz): Window Functions for Data Analysis with Postgres postgr.es/p/6Df

I am thrilled to announce that my book, Functional Design and Architecture, has just been released by @ManningBooks! FINALLY RELEASED!!! 😃😃😃😄😊😊❤️❤️❤️❤️❤️❤️ This has been a long journey, and I sincerely hope this book will make a significant contribution to the functional programming world. 🎇🎇 ❓ Who is this book for? It's for all developers interested in practical functional programming. This book is useful for software architects, senior developers, and everyone else. The model language is Haskell, but the ideas are universal and applicable to languages like Scala, OCaml, F#, and even C# and C++. ❓What is this book about? It’s about applying an engineering approach to functional programming. Design patterns, design principles, application architectures, best practices, approaches, and deep ideas—all combined into a comprehensive and highly consistent methodology for building real-world applications. 📔 Functional Design and Architecture is structured, consistent, well-written, and approachable. I’ve made a special effort to ensure the content is accessible to a wide audience. The narrative is engaging, free of jargon and complex mathematics, and progresses in a friendly, gradual manner. 💡 The ideas are universal; some were known before, but many were developed throughout this project. There was a significant knowledge gap, and this book covers much of it for our benefit. A titanic amount of work went into this book. Specifically, the following were created: 🟠 A full-fledged application framework, Hydra; 🔴 A proof-of-concept platform for creating spaceship management scenarios; 🟡 The methodology of Functional Declarative Design, covering various aspects of design and software architecture in functional programming; 🟢 A unique architectural approach, Hierarchical Free Monads; 🔵 A multitude of new design patterns, approaches, and practices, in addition to those that already existed; 🟣 Several demo applications, included both in the book and in the Hydra framework; 🟤 A wealth of accompanying material: articles, talks, and side projects; ⚪️ And of course, these ideas have been successfully tested in practice in several places. You'll also find many links to other valuable resources in this book because the subject is very broad and deep. I am especially grateful to all those who initiated this movement toward the practical application of functional programming. I stand on the shoulders of giants and deeply appreciate their contributions. On the cover, you’ll find testimonials from these distinguished individuals: 🟡 @ScottWlaschin, author of Domain Modeling Made Functional (Pragmatic Bookshelf) 🟤 @debasishg, author of Functional and Reactive Domain Modeling and DSLs in Action (both from Manning) 🟣 @VBragilevsky @_bravit , author of Haskell in Depth (Manning) I hope you enjoy the book as much as I enjoyed writing it. Bon voyage!

Learning Haskell/FP often expands people’s minds. In a world dominated by Java + Python intro courses, being forced to see computation in a new way is very empowering. There’s almost no downside to learning these techniques and having them in your toolbox.

Want to learn how database concurrency control really works? Check out this paper from @YingjunWu and @andy_pavlo!  It dives deep into the most widely used type of concurrency control today: multi-version concurrency control (MVCC). The basic idea behind MVCC is for a database to store multiple versions of each data item so that transactions can read from items being written to by other transactions. This can greatly improve transaction throughput by allowing any number of reads to occur concurrently with a write. Of course, there are many ways to implement MVCC, and the paper describes several of the most popular approaches and their tradeoffs, with detailed experiments to show how much those tradeoffs matter in practice. When I was working on concurrency control in grad school, I spent a lot of time looking at this paper and its references to learn the field!

It took three years to finish, but our follow-up to the 2006 "What Goes Around Comes Around" is finally out! Stonebraker and I examine the last 20 years in databases and discuss why relational databases + SQL will continue to remain on top. 📄PDF: db.cs.cmu.edu/papers/2024/wh…

Published a new blog post! ✍️ 8 months of OCaml after 8 years of Haskell in production In this blog post, I compare OCaml and Haskell across 🧪 Syntax 🧪 Features 🧪 Ecosystem 🧪 Tooling 🧪 Compiler messages 🧪 Standard library I hope you enjoy! 🤗 And let me know any feedback you have! Please, repost to support my work! Really appreciate that! 🙏 dev.to/chshersh/8-mon…

Introducing NeoHaskell: A beacon of joy in a greyed tech world dev.to/neohaskell/int… #haskell #opensource #programming

"FoundationDB: A Distributed Key-Value Store", from this month's CACM, is a great read. Well worth checking out for anybody who works on the architecture of large systems: cacm.acm.org/magazines/2023…

10 Haskell/GHC features I avoid: >>= ; let if-then-else case-of import data type class instance They’re not always a problem. But, they’re overused, and can often be replaced by better alternatives. Here's why I avoid each, and what I do instead... 📷

New blog post: Things DBs don't do - But should! thenile.dev/blog/things-db… It is based on my keynote at #ddtx23 - lots of people asked about it and there were no recordings. So I put my thoughts on writing.