Barry O’Sullivan

86 Meadowgate, Gorey, Co. Wexford

Software Engineer • Team Lead • Architect • DDD Specialist • Conference Speaker • Event Organiser

About me

Staff engineer experienced in high traffic financial systems (371M sales PY, $2.8B in revenue). Architected & implemented multiple products for companies of all sizes. Works in existing/legacy codebases & elegantly evolving those systems to meet new business needs. I'm empowered by working with & growing team members, as I believe that we can go further together.

Skills

Development

  • PHP (19yr)
  • JAVA (10yr)
  • SQL (19yr)
  • HTML/CSS (19yr)
  • JS (16yr)

Dev Practices

  • CI/CD
  • Agile development
  • Scrum/Kanban
  • Event Storming
  • Feature flags

Architecture/Design

  • Evolutionary design
  • Event Driven
  • Event Sourcing
  • TDD
  • DDD

Platforms/Frameworks

  • GCP
  • AWS
  • Laravel
  • Spring
  • React

Core Competencies

  • Goal orientated
  • Metric driven
  • Clear communicator
  • Mentoring
  • Pragmatic design

Employment

Etsy Payments: Staff Software Engineer on the Payments Compliance & Tax Team (2021 - 2025)

Staff engineer & team lead for 9 engineers. Responsible for designing, building, maintaining & evolving all tax & payments compliance systems at Etsy. Worked with product/leadership to map deliverables & timelines, with little to no downtime.

  • PCI 4.0 Compliance: Planned & executed a modular, self contained, React powered, credit card entry system via a micro-service, minimising compliance overhead & ensuring 2025. certification and $2.8B in revenue
  • 1099k Compliance: Ensured 5.1M US sellers have verified SSN/EINs to meet new legislation under tight time constraints, required full map of legacy systems and extensive refactoring. Automated all generation of 1099ks.
  • Bank Account Verification: Integrated with Plaid and reverfified 1.8M bank accounts in 6 months. In-depth system mapping, UI changes, refactoring, customer communication, real-time tracking/monitoring, leading to no loss in revenue.
  • Inform Act: Reimplemented our identity system with product to gather required data for 5M US sellers, analsyed disparate data sources and discovered/fixed numerous security holes and compliance oversights
  • Tax Calculation: Integrated with Vertex, sending nuanced contextual information (ask me about Canada), ensuring orders are taxed appropriately in real-time for countires worldwide, with 950M requests PY.

PHP Consultant, Architect & Contractor (2018 - 2021)

Independent consultant for theJournal.ie, Adverts.ie & Daft.ie, all highly regarded & high traffic Irish websites. Specialised in legacy web apps, reverse mapping product behaviour & adding new functionality in an iterative, testable & stable manner. Liased with dev managers to upskill their team in design, refactoring & architecture skills.

  • SCA Compliance: Replaced entire payment system with Stripe 2FA iteratively with zero downtime.
  • Cross-selling: Designed & executed a highly profitable, async message backed, cross share system between products
  • Upsells: Introduced “Orders” iteratively to web & mobile apps so multiple products/upsells could be purchased at once.
  • Responsive Migration: Planned & implemented iterative migration of legacy (12yr+) codebase to responsive layouts.
  • Training: Upskilled dev team in clean architecture, testing & legacy refactoring.

Dynamic Reservations: Lead Engineer/Architect (2016 - 2018)

Architected an event sourced product, leading 5 engineers, in the travel agency space. Upskilled the team in event sourcing & domain exploration, ensuring we had the skills to execute & build a scalable SPA.

Education

Trinity College Dublin (2008 - 2009)
Msc Computer Science
Trinity College Dublin (2004 - 2008)
BA(mod) Computer Science