Amaury M, Developer in Paris, France
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Amaury M

Verified Expert  in Engineering

Blockchain Developer

Paris, France
Toptal Member Since
March 15, 2017

Amaury is a certified senior Toptal blockchain engineer working as a protocol developer on the Cosmos SDK. Previously, he spent three years focusing on core development on Polkadot, Substrate, and Ethereum. Amaury is interested in entrepreneurship and has worked for startups of various sizes. In his spare time, he is interested in multiple subjects, such as mathematics, history, and philosophy.


Regen Network (Cosmos SDK Team)
Blockchain, Go, Cosmos
Parity Technologies
Ethereum, Parity Polkadot, Rust, Blockchain, WebAssembly, Open Source, Web3.js...
Web3.js, Ethereum, DApps, Blockchain, Full-stack Development




Preferred Environment

Blockchain, Parity Polkadot, Cosmos, Ethereum

The most amazing...

...project I've built was a mobile app that got featured on NBC and BBC with 100,000+ users. It was built in one weekend!

Work Experience

Senior Blockchain Engineer | Cosmos Core Developer

2020 - 2023
Regen Network (Cosmos SDK Team)
  • Played a key role in driving the ongoing evolution of the Cosmos blockchain ecosystem by developing the Cosmos SDK, consistently placing among the top three most active contributors throughout my tenure.
  • Spearheaded the end-to-end design and implementation of critical Cosmos protocol upgrades, such as SIGN_MODE_TEXTUAL, resulting in a significant enhancement of hardware wallet UX and security.
  • Architected and implemented significant upgrades to the Cosmos SDK, such as introducing Protobuf as the default encoding while maintaining backward compatibility.
  • Conducted educational workshops, tutorials, and webinars to empower developers and the broader community with insights into the Cosmos SDK and its capabilities.
  • Actively engaged in on-chain governance, contributing to and voting on critical network upgrades and decisions that shape the future of the Cosmos ecosystem.
Technologies: Blockchain, Go, Cosmos

Blockchain Engineer

2017 - 2020
Parity Technologies
  • Headed the development of a proof-of-concept crypto wallet running a Polkadot light client in WebAssembly inside the browser.
  • Refactored Polkadot.js (100,000 lines of code), the official TypeScript SDK on top of Polkadot and Substrate, into a more modular architecture with dynamically-generated TypeScript typings.
  • Created and launched Fether, the first Ethereum wallet on top of a light client, totaling 5,000 downloads after one year.
  • Designed and completed Light.js, a high-level reactive library optimized for light clients and an alternative to Web3.js.
  • Presented talks about Web3.js, DApp development, and light clients.
  • Cooperated with security firms on auditing the Polkadot.js codebase.
  • Integrated the low-level in-house codec, SCALE codec, into the Polkadot.js codebase.
Technologies: Ethereum, Parity Polkadot, Rust, Blockchain, WebAssembly, Open Source, Web3.js, Smart Contracts, Substrate

Full-stack Developer

2017 - 2017
  • Led the development of a RESTful Express server that connected to the Ethereum blockchain using web3.js.
  • Architected and developed an innovative one-click, cryptographically-secure login flow using the MetaMask extension. See the associated article on Toptal Blog:
  • Wrote tests that covered 98% of the codebase and set up a git-based continuous integration using CircleCI, which deployed staging and production versions to AWS.
  • Built the front-end web app skeleton using React and Redux and delegated further front-end development to a junior developer.
Technologies: Web3.js, Ethereum, DApps, Blockchain, Full-stack Development

Full-stack Developer

2017 - 2017
  • Emphasized UX by paying extra attention to details, as UX is one of Fieldbook's strengths.
  • Participated in the team-wide project of shipping version 2.0 of the product, working under high pressure for the whole month preceding the launch.
  • Collaborated with the product owner, developers, and QA engineers in an agile environment.
  • Wrote at least one line of test for each line of code.
Technologies: Full-stack Development

Lead iOS Engineer

2017 - 2017
  • Reorganized the code by introducing the Ducks architecture for Redux, increasing the readability and maintainability of the codebase.
  • Transitioned from REST API calls to GraphQL queries, optimizing network payloads, especially for low-bandwidth mobile phones.
  • Created a customizable three-part screen component for an innovative UX, with a new way of navigating between screens.
Technologies: React Native

Lead Front-end Engineer

2016 - 2016
  • Completely redesigned the landing page—resulting in a 30% conversion rate increase.
  • Built from scratch, the back office led to a huge productivity boost compared to the previous Trello-based system.
  • Assembled build tools (Gulp, Jenkins) to automate and optimize website building, testing, and deployment.
  • Conducted A/B testing on landing page features to obtain the highest conversion rate.
Technologies: Full-stack Development

Software Engineer

2014 - 2014
  • Created from scratch a Chrome extension for bookmarking; it was rated five stars and used by 250,000 users in the Google Chrome Store.
  • Led the development of the Feedly macOS app. While the app itself consisted only of a WebView wrapper over the main website, I implemented multiple features for a native-like user experience.
  • Built a prototype of—an easy way to add RSS feeds to your favorite news aggregator.
  • Worked closely with the designers to implement new UI/UX features on the main page
Technologies: Full-stack Development

Cloud Computing Intern

2013 - 2013
  • Conceived and implemented tailored IaaS solutions for client companies such as Danone and Gemalto using VMware.
  • Optimized the virtual machine creation process, reducing the VM installation time from eight hours to 45 minutes.
  • Created a UI for following in real-time the VM creation process.
  • Documented the VM creation tool usage guide in detail, both for end-users and developers.
Technologies: Linux Server Administration

Linux Adminstrator

2011 - 2013
VIA Centrale Réseaux
  • Oversaw the whole network at the university campus with 6,000 connected devices.
  • Managed a five-person team on a Linux server administration (Apache, Postfix, BIND, and virtualization).
  • Built from scratch the local Facebook of the university, using Symfony 2, PostgreSQL, and jQuery; it had 3,000 daily active users.
  • Launched an ICEcast radio streaming platform for the university.
Technologies: Linux Server Administration

Sh**t! I Smoke
A free and open-source web and mobile application that lets you see your city's air pollution measured in daily cigarettes—the app has 100,000 installs and was featured on NBC, BBC, HuffPost, and CityLab.

As an indie founder, I bootstrapped Reacher, a SaaS for email verification, generating $10k ARR after my first year. Built upon the home-grown open-source Rust library, `check-if-email-exists` (3k+ stars), the software focuses on performance and concurrency.

Feedly Mini

A Chrome browser extension that keeps you connected to your Feedly—allowing you to save easily, tag, share, or subscribe to the high-quality content you find each day. It has ~250,000 users and is rated five stars.

In The Loop

This project involved a Salesforce productivity app that uses gamification. I built the demo version of the app during a two-day hackathon organized by AXA.

My group won first prize at the hackathon.


Go, TypeScript, Rust


Parity Polkadot, React Native




Blockchain, Ethereum


DApps, Cryptocurrency, Open Source, Smart Contracts, Cosmos, Substrate, Linux Server Administration, WebAssembly, Full-stack Development

2015 - 2016

Master of Science (Double) Degree in Computer Science

Wrocław University of Science and Technology - Wrocław, Poland

2011 - 2016

Master of Engineering (Double) Degree in Engineering and Management

Ecole Centrale Paris - Paris, France


Machine Learning Course Certification

Stanford University via Coursera