Sean Marjason, Developer in London, United Kingdom
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Sean Marjason

Verified Expert  in Engineering

Software Developer

London, United Kingdom
Toptal Member Since
October 31, 2022

Sean designs and builds digital products and has worked with several big corporations, focusing on delivering bespoke applications with teams who value innovative results over processes or policies. He has ten years of experience as a Software Engineer, working with the latest tools like React, Node.js, and AWS, identifying what users need, and designing product iterations that feed insights into the design loop.


React, Next.js, Node.js, SCSS, TypeScript, Amazon Web Services (AWS), Jest...
Business Analysis, IT Business Analysis, User Research, Process Design...
BNP Paribas
Requirements Analysis, Business Process Analysis, Data Analysis, Business Cases...




Preferred Environment

Visual Studio Code (VS Code), InVision, Slack, Balsamiq Mockups, Excel 365, Amazon Web Services (AWS), Chrome

The most amazing...

...thing I've developed is a toolset for UK Clinicians to help them respond to the COVID-19 pandemic.

Work Experience

Software Engineer

2020 - PRESENT
  • Worked as a Software Engineer in full-stack web application development with React and Node.js, hosted on AWS.
  • Led development of a new user interface for the internal environment dashboard, tracking the deployment status and condition of three separate projects, each managing around 15 environments.
  • Supervised the UI maintenance team for a clinical tool developed for the NHS response to the COVID-19 pandemic, including a risk assessment journey and login solution hosted on AWS, supported by a wider team of approximately five developers.
  • Managed the transition to a monorepo approach for a workstream at the above NHS project to support transitioning the platform to a modular, reusable codebase that would be deployed in future pandemic responses supporting the new user journeys.
  • Organized delivery of integration of clinical tools with external COVID-19 infection data to support new algorithm inputs, including requirement analysis and process design to avoid breach of API rate limits.
  • Developed rapid prototyping of gamified developer recruitment and onboarding experience using an internal chatbot platform integrated with a web interface built in p5.js.
  • Secured a contract for further work with a large UK insurance provider.
Technologies: React, Next.js, Node.js, SCSS, TypeScript, Amazon Web Services (AWS), Jest, WebdriverIO, GitLab, HTML, CSS, JavaScript

Business Analyst

2018 - 2020
  • Contracted business analyst and agile specialist helping clients to establish product roadmaps, embed agile practices, identify and refine requirements, conduct user research, create user stories, and manage project software and development teams.
  • Delivered a bespoke, production-grade global chatbot platform servicing around ten client teams over 18 months, including leading a pivot to an advanced conversational flow pattern delivered ahead of market-standard platforms to meet user needs.
  • Redesigned the user experience and web UI for a complex content management system for the above chatbot platform, introducing market-leading conversation design principles to enable non-technical users to create chatbot content independently.
  • Led a three-month initiative to consolidate the internal business analysis knowledge base for BJSS, leading to more consistent working practices and improved onboarding experience for new staff.
  • Defined the baseline reporting and control function in data science for a major UK retail bank for the first production-scale data science project.
  • Returned a compliance project with a six-month delay to completion within five months by refining scope using transactional data collated from six disparate business lines and applications.
Technologies: Business Analysis, IT Business Analysis, User Research, Process Design, Requirements Analysis, SQL, HTML, CSS, JavaScript, React, Agile, UX Design, Cloud Computing, Sketch, InVision

Business Analyst and Project Manager

2015 - 2017
BNP Paribas
  • Led projects as the principal business analyst for corporate and institutional banks in Sydney, collaborating with the COO's portfolio of change initiatives, including team, restructures, process redesign, and software deployment.
  • Created the switch to automated expense reimbursement and travel booking with the migration of Australia and New Zealand from paper-based processes to Concur SaaS application.
  • Enabled the renegotiation of supplier contracts by establishing a procurement function for Australia and NZ and implementing SAP ARIBA contract management solution, enabling data capture and analysis of supplier contracts and spending.
  • Facilitated the Sydney branch to become the global case for Robotic Process Automation (RPA) technologies by identifying a backlog of around 20 efficiency and staff capacity-building opportunities.
Technologies: Requirements Analysis, Business Process Analysis, Data Analysis, Business Cases, IT Project Management, Software Requirements Specifications (SRS), Software Release Management

Senior Analyst

2014 - 2015
  • Worked as the Senior Analyst for assurance and advice on the effectiveness of systems, processes, and controls across the corporate and institutional bank, focusing specifically on operational risk and end-user computing.
  • Led the successful recovery of a key assurance project facing a three-month delay by redefining the scope and approach by removing repetition through analysis of controls data to identify the redundant workload.
  • Revised the business process architecture for all key institutional bank processes, integrating process and control information into a single source leading to a reduced workload for the assurance team when planning and scoping assurance projects.
Technologies: Risk Analysis, Controls, Data Analysis, Project Management, Business Process Analysis, Systems Analysis, Data Modeling

Senior Consultant

2010 - 2014
PwC Australia
  • Managed client engagements specializing in business process analysis, controls assurance, information technology, project assurance, and project cost control.
  • Triggered the release of funding to regional councils across Queensland for capital project works by assuring the use of state funds for rehabilitation works in remote communities.
  • Produced an approach to internal audits across Australian offices as the delivery lead for the Brisbane Office's revised internal audit methodology and tools.
Technologies: Business Risk Assessment, Controls, Business Process Analysis, Data Analysis, Systems Analysis

COVID-19 Clinical Tool

Designed this tool for use by clinicians during a consultation with a patient, allowing for an assessment of a patient's risk of complications if they were to contract COVID-19.

My involvement in this project focussed primarily on taking the initial generic tool built to support the pandemic and identifying and implementing ways in which the tool could be adapted to help other potential future pandemics. This was in addition to iterating the existing tool to support newly identified requirements gathered through engagement with clinicians.


Requirements Analysis, Agile, ETL, Object-oriented Programming (OOP), UX Design

Industry Expertise

Project Management


Business Process Analysis, Business Analysis, Web Development, Excel 365, Business Systems, Financial Accounting, Management Accounting, Statistics, Data Analysis, Information Systems, Reporting, Economics, Algorithms, Regression, Classification, Programming, Networking, Mathematics, Business Risk Assessment, Controls, Systems Analysis, Risk Analysis, Data Modeling, Business Cases, IT Project Management, Software Requirements Specifications (SRS), Software Release Management, IT Business Analysis, User Research, Process Design, Cloud Computing


JavaScript, HTML, CSS, SQL, Python, R, C++, SCSS, TypeScript


Next.js, Chrome, Jest


React, Node.js


InVision, Slack, Balsamiq Mockups, Sketch, WebdriverIO, GitLab


Jupyter Notebook, Amazon Web Services (AWS), Visual Studio Code (VS Code)


Databases, PostgreSQL

2020 - 2022

Bachelor's Degree in Computer Science

University of London - London, UK

2016 - 2017

Graduate Certificate in Data Science

University of Sydney - Sydney, Australia

2009 - 2011

Bachelor's Degree in Accounting

Queensland University of Technology - Brisbane, Australia

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