Arda Karaduman

Before Veltra I built and ran Go, Ruby, and Python systems for logistics, fintech, medical IT, and game companies. I have been in Tokyo since 2004 and act as the bridge between overseas and Japan teams, in English and Japanese.

Systems Architect · Veltra · Tokyo, Remote

Systems architect at Veltra working across Python, Go, and Node services and AWS infrastructure, including MCP services that expose the travel-activity catalog to AI assistants and internal analytics tools.

• Built a stateless 'activity search' MCP server that runs in both Claude and OpenAI app hosts. Anthropic approved it and it is listed in the public Claude connector directory. Also built internal read-only MCP tools for Google Analytics and AWS.
• Moved image delivery off a paid CDN onto an in-house setup on AWS CloudFront.
• Application and infrastructure architecture for the Python, Go and Node services, which deploy to AWS ECS through Terraform and GitHub Actions.
• Bridge engineer between the overseas and Japan teams; led the MCP integration of legacy systems.

Senior Developer · Gaussy · Tokyo, Remote

Senior backend engineer and top-3 author on the Go (Echo/GORM) API behind WareX, a production logistics 'warehouse-exchange' SaaS. Owned core domain areas and the team's integration-test harness.

• Senior backend engineer and a top-3 author on the Go (Echo / GORM) API of WareX, a production logistics 'warehouse-exchange' SaaS (the company incorporated as Gaussy in 2022).
• Owned the warehouse (geo- and license-filtered search), contract, workspace, document and price-specification resources, from data models to REST endpoints and migrations.
• Built role-based access-control middleware and server-side mass-assignment guards, plus request validation and parameterized queries.
• Owned a large share of the integration-test suite, including the shared test harness the rest of the team's API tests run on.
• Database migration and seeding (goose) and Bugsnag error reporting; third-party integrations including Hubspot and Mailgun.
• Deployed on Google Kubernetes Engine via CircleCI with SOPS-managed secrets; some frontend work on the Vue/Nuxt admin and customer portals.

Senior Developer · Robotfund · Tokyo, Hybrid

Lead developer of a LINE-bot fintech platform (Rails 5 + React) and a race-free Go media/TTS caching service for a Tokyo robo-advisory startup.

• Lead author of a multi-tenant Rails 5 JSON:API + React platform delivering fund and bond analytics (net-asset-value graphs, factor analysis) to users as LINE Flex Messages and generated charts.
• Implemented LINE webhook HMAC signature verification, strong-parameter authorization across all controllers, and bcrypt-secured authentication.
• Built, alone, a Go service in front of a pool of text-to-speech servers: channel-owned state with no data races (checked with `go test -race` in CI), PCM-to-MP3 transcoding, content-digest caching and per-host load distribution.
• Built a Go AWS Lambda ingesting daily Reuters DataScope Select market data into an idempotent DynamoDB/S3 state machine, and extracted an MIT-licensed Reuters DSS Go client library.
• CI/CD on CircleCI: builds and deploys, Docker images pushed to AWS ECR, releases gated on tags.

Senior Development Engineer · Allm Inc · Tokyo, Onsite

Sole or lead developer on two product lines at a medical-IT and retail-analytics company: an IoT/edge people-analytics product and a versioned stroke/cardiac triage API for hospitals.

• Sole author of a Go daemon for in-store edge devices (amd64 and ARM) that counted staff via BLE beacons and repeat customers via WiFi sniffing, ran face recognition, and had a web configuration UI.
• Built its full over-the-air update pipeline: cross-compiled amd64/armhf, built signed Debian packages, pulled build secrets from HashiCorp Vault, GPG-signed releases, and published to an S3 apt repository with testing/release channels.
• Lead author of a FAST-ED stroke/cardiac triage API for hospitals (Ruby/Grape + GraphQL + Pundit) with API versioning, HMAC request signing, and bcrypt auth with login lockout and rotating keys.
• Co-built the triage admin SPA (Vue 2 + Apollo) deployed to AWS S3/CloudFront, and contributed sensor-vendor drivers to a multi-tenant Go ingestion daemon.
• Extracted reusable Go libraries to my own namespace; CI/CD with GitLab CI and Docker.

Developer · Aiming Inc · Tokyo, Onsite, Contract

Backend engineer on the live Ruby/Padrino backend of a mobile MMORPG published in Japan and Korea; owned several gameplay features on my own.

• Backend engineer on the live Ruby/Padrino backend of 'Griffon', a published mobile MMORPG (Japan + Korea/Naver) in a ~60-engineer codebase.
• Owned the achievements, friendship, reward-distribution and guild-battle matchmaking systems on my own: data model, typed-RPC service, master-data importer, migrations and tests.
• Designed database-level idempotency via unique indexes and wrapped multi-step in-game economy mutations in transactions.
• Built a typed-RPC API with server-side authorization whose structure rules out mass assignment, covered by RSpec suites that exercise every branch.
• Shipped to tight Agile deadlines on a game with thousands of daily active users.

Dev Ops · Kii Inc · Tokyo, Onsite

Owned the usage-metering and billing pipeline for a mobile Backend-as-a-Service platform, plus the API gateway and Puppet deployment around it. Also wrote the team's first Go code.

• Co-led, as primary author, a Ruby usage-metering and billing batch for a mobile Backend-as-a-Service platform. It aggregated per-app API, storage and analytics usage from a 3scale API gateway, computed plan overages, and reported billable usage to Zuora with idempotent create-or-update reconciliation.
• Tested with RSpec, Minitest and serverspec; packaged as an Omnibus/RPM cron job.
• Built and operated the Varnish + 3scale API-gateway metering layer and the Puppet modules (VCL/Puppet) that deployed the billing and gateway stack.
• Payment integration via Zuora and PayPal; usage tracking and logging with 3scale, Varnish and fluentd.
• Developer-portal development (Ruby on Rails, Backbone.js) and Cloud Code maintenance (Node.js); wrote the team's first Go code (an early Kii Go SDK).
• Automated reports and AWS resource tuning in Ruby and Bash, with Puppet.

Dev Ops · Mobilous Inc · Tokyo, Onsite

Sole build/release and cloud-infrastructure engineer for a white-label no-code mobile-app platform: the native build pipeline, S3 release delivery, and Puppet/Vagrant provisioning.

• Sole build-and-release / cloud-infrastructure engineer for AppExe, a white-label no-code mobile-app builder that generated native iOS/Android apps.
• Built the on-demand native build service that turned no-code app definitions into signed native APKs (Ruby/Sinatra, with a Python predecessor).
• Authored full server-stack provisioning with Puppet + Vagrant (dual VirtualBox/AWS): GlassFish, PostgreSQL, MongoDB, log shipping and firewall, plus the Android/iOS build, release and backup scripts.
• Built a per-customer AWS account/instance activation control plane and a versioned S3 release-delivery tool.
• Automated AWS account signup end-to-end with a Selenium-driven pipeline, and ran the team's git server.
• Designed the EC2 infrastructure, with monitoring and auto-scaling.

Contract Developer · Ryde Inc · Tokyo, Remote - Part Time

Part-time backend (and some frontend) development for Ryde's mobile and web services using Ruby on Rails and GraphQL.

• Backend development for Ryde services (Mobile and Web) using Ruby on Rails and GraphQL.
• Some frontend development (Admin site, Ruby on Rails, React).

Contract Developer · Iron.io · US, Remote - Part Time

Part-time open-source contributor to the web UI and engine of IronFunctions, an early Docker-based serverless (FaaS) platform.

• Part-time open-source contributor to IronFunctions, an early Docker-based serverless (FaaS) platform (later the Fn Project).
• Top-3 author of the IronFunctions web UI (Express + Vue), which I also helped maintain. Added JWT authentication and the CI/CD Docker release pipeline.
• Contributed features and fixes to the Go FaaS engine, including a payload-as-stdin runner and a dependency-management migration.
• Wrote example serverless functions in Go, Node and Ruby to dogfood the platform.

Travel Activity MCP Services

MCP services at Veltra that expose the travel-activity catalog to Claude and ChatGPT apps, plus internal analytics tools. The activity-search connector is listed in Anthropic's public Claude connector directory.

• Python
• FastAPI
• Model Context Protocol
• Terraform
• AWS ECS

WareX — Logistics SaaS API

Senior backend engineer and top-3 author on the Go API of WareX, a production logistics 'warehouse-exchange' SaaS at Gaussy. Owned the warehouse, contract, workspace, document and pricing resources and the team's integration-test harness.

• Go
• Echo
• GORM
• MySQL
• JWT/RBAC
• Minio/S3
• GKE
• CircleCI

golem — LINE-bot Fund Analytics

Lead author of a multi-tenant Rails 5 + React platform that delivers fund and bond analytics (net-asset-value graphs, factor analysis) to users as LINE Flex Messages and generated charts, with HMAC webhook verification, at Robotfund.

• Ruby on Rails 5
• React
• JSON:API
• LINE Messaging API
• gnuplot

bumblebee — Race-free TTS Caching Service

Go service written alone at Robotfund, in front of a pool of text-to-speech servers: channel-owned state with no data races (verified with `go test -race`), PCM-to-MP3 transcoding, content-digest caching and per-host load distribution.

• Go
• CSP concurrency
• LAME (PCM→MP3)
• Docker
• AWS

Reuters Market-Data Pipeline

Solo Go AWS Lambda that ingests daily Reuters DataScope Select market data into an idempotent DynamoDB/S3 state machine, built on an extracted MIT-licensed Reuters DSS Go client library, at Robotfund.

• Go
• AWS Lambda
• DynamoDB
• S3
• Reuters DataScope Select

github.com/c0ze/dss_reuters_go ↗

FupIntuition — IoT/Edge People Analytics

Sole author, at Allm, of a Go daemon for in-store edge devices that counts staff via BLE and repeat customers via WiFi and runs face recognition, with a web UI and a signed over-the-air update pipeline.

• Go (amd64 + ARM)
• BLE beacons
• WiFi sniffing
• HashiCorp Vault
• GPG-signed OTA
• S3 apt repo

FAST-ED Clinical Triage API

Lead author, at Allm, of a versioned stroke/cardiac triage API for hospitals (Grape + GraphQL + Pundit), with HMAC request signing and bcrypt authentication with login lockout. Co-built its Vue 2 + Apollo admin SPA.

• Ruby
• Grape
• GraphQL
• Pundit
• HMAC
• bcrypt

Griffon — Mobile MMORPG Backend

Backend engineer at Aiming on the live Ruby/Padrino backend of 'Griffon' (幻塔戦記グリフォン), a mobile MMORPG published in Japan and Korea. Owned the achievements, friendship, reward-distribution and guild-battle matchmaking systems, with idempotency enforced in the database.

• Ruby
• Padrino
• ActiveRecord
• MySQL
• Resque
• RSpec

IronFunctions — Open-source Serverless Platform

Open-source contributor to IronFunctions at iron.io, an early Docker-based FaaS platform (later the Fn Project). Added JWT auth and the CI/CD release pipeline to its web UI, and engine features such as a payload-as-stdin runner.

• Go
• Docker
• Vue
• Express
• JWT
• CircleCI

github.com/iron-io/functions ↗

This Résumé Site

Static résumé site in English, Japanese and Turkish, prerendered to HTML. One content source produces the page and the PDF, DOCX, JSON Resume and vCard files at build time; hosted on GitHub Pages.

• ReScript
• React
• Vite
• Tailwind CSS
• PDFKit
• docx

github.com/c0ze/resume ↗

Master of Science · Keio University

Graduate research at the Amano Laboratory (computer architecture / embedded systems / VLSI). Completed the Master's in 2008 and continued PhD-level research through 2011 — four first-author peer-reviewed papers on the "Echo instruction," a hardware code-compression technique implemented in Verilog on a MIPS R3000 core and synthesized to 90nm silicon — before moving to industry.

Master's thesis ↗

Bachelor of Science · Istanbul Bilgi University

Dissertation on parallel simulation of quantum circuits on Linux clusters (MPI) — implementing the QFT, Grover and Shor algorithms with a distributed state-vector simulator.

Dissertation ↗