About

I'm Bui Duc An, a senior backend engineer based in Ho Chi Minh City. I've spent the last decade on one platform: a JFSA-licensed crypto exchange that changed hands from Liquid to FTX Japan, then to bitFlyer's Custodiem. The technology stack rotated (Ruby, Python, C#), the owners changed, the regulator did not, and neither did the obligation to keep customer money safe.

Early on I led the engineering behind Liquid's JFSA licence application in 2017, after two outsourced attempts had failed. That meant designing the regulatory reporting architecture, building the nightly jobs in Rails and Sidekiq, and then living with them for the next five years under audit. When FTX collapsed, I worked on Project Revival's balance-confirmation flow, specifically the balance-verification component and the identity matching between the FTX and Liquid ledgers that had been merging before the collapse. The overall design was owned by my boss and the team; the flow reopened on 21 February 2023 and returned roughly US$140M in customer assets, the first FTX entity to give customers their funds back. Today I own the Custodiem side of a Fireblocks-integrated transaction processor built in C# to bitFlyer's design.

I care about backend systems that survive one operator: idempotent writes, real reconciliation, a compact test surface that gates production changes, and code that a new engineer can read on their first day. My best work has been the kind that stays boring under regulatory scrutiny.

Career

• — Aug 2024 – present · Custodiem Inc. (bitFlyer Group, formerly FTX Japan). Senior Software Engineer. C# / Python / PostgreSQL / AWS / K8s / Fireblocks.
• — Jul 2022 – Aug 2024 · FTX Japan. Senior Software Engineer. Owned balance verification and FTX–Liquid user matching inside Project Revival (~US$140M returned to customers). Python / PostgreSQL / AWS.
• — Jun 2016 – Jul 2022 · QUOINE / Liquid. Software Engineer → Senior (2018). Led JFSA licence engineering. Rails / PostgreSQL / Redis / Sidekiq / Lua / AWS.
• — Oct 2014 – May 2016 · NUS Technology, HCMC. Full-stack Rails.

Stack

Languages: Ruby (8 yrs), Python (4 yrs), C# (since 2024), SQL, JavaScript, Lua.
Ruby / Rails: Rails, ActiveRecord, Sidekiq, RSpec, REST API design, Redis.
Data & infra: PostgreSQL, AWS, Kubernetes, Docker, CI/CD.
Domain: JFSA regulatory reporting, KYC/AML (eKYC, World-Check), Fireblocks custody, fiat payment rails, crypto exchange operations.
Observability: New Relic, Sumo Logic, Airbrake.

Working with me

Ho Chi Minh City, UTC+7. Office-based through 2022, hybrid since, working with a Japan-headquartered team. Distributed collaboration with colleagues in Japan and Singapore throughout. I'm comfortable adjusting core hours to match a team's standup and review windows.

Open to remote contractor or EOR engagement (Deel, Remote.com, Multiplier, and similar). Not looking for relocation or a visa route right now. My family is here in Saigon.

I also run a live-money crypto trading bot as a personal project. It's closed-source (the strategy is proprietary), but I'm happy to walk through the architecture and the failure modes of trading against a real exchange in conversation.