3ep.dev

SOFTWARE ENGINEERAMSTERDAM, NL

Sepehr Mohammadi

I build payment and crypto infrastructure at Bitvavo, distributed systems where the real problems only show up under load.

I'm also co-founder of Cask Studio, an AI-native video studio for the Mac: an infinite storyboard canvas, a multi-track timeline, and an agent that can edit beside you.

The rest goes into small apps I ship under my own name and music I write as septimbre.

See the work
Sepehr Mohammadi on a bridge over the Moselle, Cochem
SEPEHR MOHAMMADI52.37° N

/apps

SMALL THINGS I SHIP UNDER MY OWN NAME

  • Yetly

    The small things you do again and again. It tells you once, gently, and then it leaves you alone.

    Open

  • Chalk

    A counter where the number is money. Tap to count, settle when you pay, and the history stays.

    Open

/work

2016 — NOW

  1. Cask Studio

    Co-Founder

    An AI-native video studio for the Mac: an infinite storyboard canvas, a multi-track timeline, 20+ generation models, and an MCP so an agent can edit alongside you. Idea to export without leaving the app.

    macOSApple SiliconVideo pipelineMCP
    Jun 2026 — nowAmsterdam

  2. Bitvavo

    Software Engineer

    Payment and crypto infrastructure: distributed services where downtime is measured in money.

    Distributed systemsNode.jsGoTypeScriptKubernetes
    Apr 2023 — nowAmsterdam

  3. Catawiki

    Software Engineer

    Redesigned how services exchanged events, which cut a long tail of inconsistencies between them. Picked up Rails in two weeks and React on the spot when the team had no frontend engineer.

    GoRuby on RailsMySQLElasticsearchBigQueryKubernetesReactGCP
    Mar 2022 — Mar 2023Amsterdam

  4. Denxa

    Software Engineer

    Built cryptocurrency wallet infrastructure and Bitcoin, Ethereum and Tron indexers behind one API, then trained the team on it. Broke a monolith into mTLS gRPC services.

    GoPostgreSQLgRPCKubernetesBlockchain indexersAWSRedis
    Sep 2020 — Jan 2022Toronto

  5. Cyntax Creative Studio

    Software Engineer

    Exchange (2018–2020): rotating wallets and crypto payments, plus the GitLab CI/CD, the ESXi hypervisor, and the Linux servers the whole thing ran on. Moved the services to stateless, dockerised deployments that could scale out.

    Commerce (2016–2018): built large parts of several online shops, a crawler that filled their catalogues automatically, and an inventory system to run them. Reverse engineered Valve’s Steam APIs to source data for a game shop.

    GoNode.jsTypeScriptPostgreSQLMySQLMongoDBRedisDockerLinuxESXi
    Jan 2016 — Aug 2020Tehran

/sound

SEPEHR + SEPTEMBER + TIMBRE

My dad played, so there was always a guitar in the house. I picked it up at eight and never really put it down. Music is what makes life worth living for me, and it's the one thing I've never needed a reason to keep doing.

Everything under septimbre is written, played and recorded in a room at home, one part at a time.

PIANOGUITARBASSDRUMSVOICE

Spotify

/photo

10 FRAMES · 2023 — 2026

Every photo here was taken on a phone. It is the camera I have on me.

Mostly on the way to somewhere else, and mostly vertical, because that is how I hold the thing.

@sepmography
  • Sun breaking through heavy cloud over the IJ, with the domes of the Basilica of Saint Nicholas in silhouette
    AmsterdamAug 2026
  • A carved stone facade beside a wall of mirrored panels reflecting it back in fragments
    ParisAug 2023
  • The Turning Torso tower seen from its base, twisting into a dark sky
    Malmö, SwedenJul 2024
  • A bicycle parked on a dike path between water and grass, under a bank of storm cloud
    Markermeer, NetherlandsMay 2026
  • Granite figures on the steps around the monolith in Vigeland Park, in black and white
    Oslo, NorwayAug 2024
  • A canal at low sun, an arched bridge in the distance and light scattered across the water
    AmsterdamApr 2023
  • A village on the edge of a lake under overcast mountains, with a church spire at the waterline
    Hallstatt, AustriaMar 2024
  • The corner of a green clad building shot from below against a clear sky
    AmsterdamAug 2026
  • A red church with a green copper dome and a clock tower, framed by leaves
    Stockholm, SwedenJul 2024
  • A square seen from above, with a gold sphere on a column and people crossing the stone
    Salzburg, AustriaMar 2024

/log

1 ENTRY

  • One site instead of four

    My apps kept accumulating domains, so they all moved here. Markdown files, no admin panel, and a player that draws the actual song.

All entries