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: 20+ generation models, an MCP so an agent can edit alongside you, and the whole path from idea to export inside one 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

    Reworked how services exchanged events, closing a long tail of cases where one service knew something another did not. 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. 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