sylvn.co
“One of the most loyal engineers I know.”
Mathieu Bour, CTO

Agency-grade software, built by one senior engineer.

I’m Sylvain, a senior full-stack engineer with 10 years of building and running products. Product, architecture, infrastructure and AI, on fixed scopes and public prices, with no account managers in between.

Book a 20-min callSee services and prices

Previously worked with

  • Zoop
  • Altitude
  • Mobula Labs
  • Riverflow
  • Fantium
  • Blackpool Finance
  • Betclic
  • Better Trade Off

How can I help

Selected work

Taken over, stabilised, shipped.

Altitude · HyperEVM trading terminal

From beta to investor-ready trading terminal

Altitude brought me in to improve their HyperEVM trading terminal and build the features it was missing. I connected it to the trading bot and rebuilt the chart and live data for speed. Five months later, the team had a fast, complete trading terminal to show investors, with market and limit orders live.

  • Tech lead
  • July – December 2025
Read the case study
Live
BBS

A fully functional trading terminal

Services

Four ways to work together

Three fixed-scope projects and a monthly subscription. Every engagement starts with the same free 20-minute call.

Rescue Sprint

Best for: an app with real users and growing problems.

Your app was built fast, by AI, an agency or freelancers, and now real users depend on it. I make it production-ready: a cleaner codebase, a smoother experience, and the bugs fixed.

  • $4,500
  • 2 weeks
  • Audit
  • Fixes
  • Tests on critical paths
  • Monitoring
  • Handover
Book a Rescue Sprint call

Custom development

Best for: teams running on spreadsheets and manual re-entry.

Web apps and internal tools that replace spreadsheets and manual re-entry, connected to your current software.

  • From $5,000
  • 4 to 8 weeks
  • $1,500 scoping, credited to the build
  • You own the code
Book a call about your build

Automation & AI

Best for: teams losing hours to repetitive admin.

One business process automated end to end: quotes, invoices, follow-ups, email triage, data entry.

  • From $4,000
  • 2 to 6 weeks
  • $1,500 scoping, credited to the build
  • You own the code
Book a call about automation

Lead & Velocity

A senior lead, without hiring full-time. For startups and SaaS teams that need senior dev expertise with an undefined scope.

$10,000per month

3-month minimum, then cancel anytime with 2 weeks’ notice.

Book a callPrefer email? Write to me
  • A senior lead who owns your code
  • Product features, architecture, infrastructure and AI
  • You set the priorities, I ship them one by one. No hours to count.
  • Written updates 2 to 3 times a week, daily if you prefer
  • No status meetings

Testimonials

What clients say

Sylvain couples sharp software instincts with an uncommon entrepreneurial mindset. One of the most loyal engineers I know.
Mathieu BourCTO, Mobula Labs and Riverflow

FAQ

Questions? Answered.

Anything else, ask it on the call.

Book a 20-min call

With a free 20-minute call. I then send a scope and a quote. Once the quote is signed and the deposit paid, I get to work and deliver async.

Got a product that needs to ship?

I work with a small number of teams at a time. If you need a senior engineer who takes full ownership, without hiring full-time, let’s talk.

Book a 20-min callEmail me

Based in France. English communication, async by default.