Migrating foundational software to the 21st century

We help teams make the move to Rust.

legacy.c potentially unsafe

                                    1 void*ptr = malloc(n * sizeof(Record));
                                
                                    2 if (ptr == NULL) {
                                
                                    3  handle_error();
                                
                                    4 }
                                
                                    5 memcpy(dst, src, n);
                                
                                    6 free(ptr);
                                        /* remember to free */

modernized.rs borrow-checked

                                    1 let mut buf = Vec::try_with_capacity(n)?;
                                
                                    2
                                        // allocation failure returned to
                                        caller
                                
                                    3dst.copy_from_slice(src);
                                
                                    4
                                        // buf dropped before return — no free()
                                        needed
                                
                                    5 Ok(())
                                
                                    6▋

-- until launch

--%

Proudly European based in Amsterdam

Member of

Enjoy cost-effective, low-risk and on-demand Rust development for your team.

Core offering

Rust development consultancy

We are the implementation partner that helps you start or accelerate the move to Rust.

Team augmentation at any stage of your project

Hands-on design and development

No long-term contracts or risky commitments

Embed

Augment your team

No-one (including us) likes know-it-all consultants. We want to work together wherever possible.

Experience

Try us

Of course it can feel tricky to work with new people, so why not work together for 30 days to see if it is a match? No commitment.

Decide

Plan a second date?

We are pretty confident that you will like our work after 30 days, but no hurt feelings if we are not the right fit for you.

No expensive middlemen or agency fees. Just work together with two talented, passionate and approachable engineers.

Systems Engineer

Elias

Finds joy in working with motivated people to solve difficult problems and is willing to break open any layer of abstraction while doing so.

elias@definedonce.com@definedtwicenow.com

Systems Engineer

Max

Holds a strong passion for programming language design and an equally strong fascination for the origins of computer architecture.

max@definedonce.com@definedtwicenow.com

+31 20 3242 150

Mon – Fri 08:00 – 18:00 CET

hello@definedonce.com@definedtwicenow.com

We typically respond within one day.

While applications evolve rapidly, the systems beneath remain trapped in antiquated languages and patterns. We rebuild those foundations so you can build on solid ground.

Our vision is shared through RFDs. Shared in public, and open to be challenged.

$ rfd list --sort=latest --limit=3 ▍

All RFDs

005 Working with Sensitive Data elias

This document describes how to handle sensitive data during our work. It does not include novel ideas, but summarizes relevant rules of thumb, tools and example…

policy

2026-02-26

004 Using Git max · elias

Source management with git allows for ample opportunity of dangerous, unhelpful or plain annoying experiences as a software engineer. While this is bad enough w…

style

2026-02-26

003 Writing Programs elias

A small collection of important thoughts on writing software. Programs must be written for people to read, and only incidentally for machines to execute. — Ger…

style

2026-02-26

We are a fully privately owned company. In our blog, we write about our work and its technical backgrounds.

All posts

Abstract visualization of a gap between private data (a sovereign cloud) and a shady corporate cloud, illustrated by a bridge between secured data storage and a crumbling bridge to a dark landscape with a cloud that shows a question mark.

April 17, 2026 company strategy

Pushing for digital sovereignty as a member of NLdigital

Why we do and do not believe that being part of NLdigital is beneficial to our values and operation.

elias

Abstract visualization of two people on a computer screen, with charts and technical icons on the background in Rusty colors.

Mar 28, 2026 company launch

Why this might be the worst time to launch a consultancy

With the world on the verge of an economic crisis and AI getting better and better, now might be the worst time to launch a development consultancy. Why are we determined to proceed anyway?