Nikolaos I. Sakellarios

Software Engineering Manager

8+ years in financial services technology — combining hands-on full-stack engineering with product ownership and team leadership. I love experimenting, learning, and building things that ship.

About

I'm a Software Engineering Manager at Santander UK Technology with a career spanning engineering leadership, product ownership, and operations management. I combine hands-on full-stack expertise (React, Node.js, Cloud, CI/CD) with a proven record of acting as Product Owner and Business Analyst — defining technical architecture, shaping product direction, and translating between technical teams and business stakeholders.

A PhD-trained analytical thinker, I deliver complex initiatives from concept to production, and I never stop experimenting with new technology.

Skills

Product & Leadership

Product OwnershipBusiness AnalysisTechnical Architecture Stakeholder ManagementAgile DeliveryTeam Leadership

Technical

JavaScript / Node.jsReactMongoDBSQL PythonC++JavaAWS TDD & BDDCI/CD (GitLab, Github, Jenkins)RubyHTML/CSS

Languages

Greek (native)English (native/bilingual)German (elementary)

Experience

Software Engineering Manager

Santander UK Technology — Research & Development
Jan 2025 – Present
  • Email Infrastructure Migration: Design and develop a Proof of Concept (PoC) to transition customer communication channels from Salesforce and Striata to AWS Simple Email Service (SES), followed by executing the full production migration.
  • High-Throughput Composition Engine: Architect and build a scalable message composition engine capable of real-time message assembly and dispatch at throughputs exceeding 750 TPS (transactions per second).
  • Referral System Integration (PoC): Lead the research, prototyping, and Proof of Concept for integrating a dedicated third-party or proprietary "Refer-a-Friend" platform into the existing ecosystem.
  • Analytics & Dashboard Modernization: Audit, redesign, and migrate existing operational and analytical reporting dashboards to a modern, unified data visualization platform.

Software Engineering Manager

Santander UK Technology — AI4Banking
Apr 2024 - Jan 2025
  • Internal Knowledge Assistant: Developed a custom Microsoft Teams plug-in enabling employees to query enterprise documents via an AI interface for rapid information retrieval.
  • Prompt Management Interface: Built a front-end application allowing staff to create, save, and deploy custom user prompts as reusable system instructions to automate and streamline daily banking workflows.
  • Fraud Simulation & Training PoC: Engineered an interactive role-playing Proof of Concept to train and assess customer support agents against emerging fraud scenarios, featuring an end-to-end voice-to-text / text-to-voice bridge alongside automated post-session performance evaluations.

Software Engineering Manager

Santander UK Technology — Chatbot | Content Editor
Nov 2022 – Apr 2024
  • Led development of the Content Editor platform (React/Node.js), abstracting GitLab and Jenkins behind an intuitive web interface to enable self-serve deployment for non-technical teams.
  • Drove dual PO/BA responsibilities: owned the product roadmap, translated business requirements into technical specs, and aligned cross-functional delivery with partner squads.
  • Architected SaaS transition: designed the initial scalable system architecture to evolve the internal Content Editor into a multi-tenant Software-as-a-Service solution.
  • Spearheaded end-to-end delivery of complex initiatives across the full SDLC, bridging cross-team engineering and customer rollout.

Software Engineer - Consultant Grade 3

Santander UK Technology — Chatbot | Content Editor
May 2021 – Nov 2022
  • Modernized chatbot content infrastructure: maintained full-stack React/Node.js applications, introducing reusable UI components and robust API integrations to enhance platform stability.
  • Streamlined content operations by modernizing the Chatbot squad's React/Node.js tooling, significantly reducing manual authoring overhead through UX enhancements.
  • Accelerated content authoring cycles by redesigning core React/Node.js tooling for the Chatbot squad, eliminating operational bottlenecks for non-technical stakeholders.
  • Partnered with content teams to iteratively refine internal tools (React/Node.js), conducting user feedback loops to deliver intuitive, high-efficiency editorial interfaces.

Software Engineer - Consultant Grade 2

Santander UK Technology — OnePayFX
Oct 2018 – May 2021
  • Architected RippleNet blockchain integration: migrated the Global Pay Outbound platform to LoopBack 4, enabling secure, low-latency settlement on distributed ledger infrastructure.
  • Engineered MongoDB & MicroStrategy data pipelines to power mission-critical reporting for enterprise fraud detection, AML/financial monitoring, and regulatory compliance.
  • Guaranteed 24/7 system reliability: orchestrated high-stakes production platform migrations and served as primary on-call for triaging, resolving, and conducting RCAs for critical live incidents.

Junior Software Engineer

Makers Academy (contractor to Santander UK) -- United Kingdom
May 2018 – Oct 2018
  • Drove core Node.js backend development for Global Pay Outbound, rolling out high-priority features while refactoring legacy codebases to systematically eliminate technical debt.

IT & Operations Manager

Pisani Plc -- United Kingdom
Feb 2011 – Jun 2017
  • Drove business transformation initiatives, establishing modernized operating frameworks that accelerated process velocity by 30%.
  • Directed IT infrastructure restructuring and successful rollout of an integrated ERP/CRM solution, generating £50k+ in recurring annual cost savings.

Product Manager

Systems Sunlight S.A. -- Greece
Oct 2008 – Dec 2010
  • Directed end-to-end product lifecycle management for UPS systems, telecom power supplies, and industrial battery chargers, cultivating key strategic partnerships to expand market footprint.

Technical Analyst / Project Manager

G.M.M. S.A. Larco -- Greece
Sep 2006 – Oct 2008
  • Streamlined operational workflows by analyzing and optimizing critical processing procedures, while spearheading strategic procurement tenders for high-spec facility and laboratory equipment.

Santander UK Technology

United Kingdom (London & Milton Keynes)

Software Engineering Manager

Jan 2025-Present
Research & Development
  • Email Infrastructure Migration: Design and develop a Proof of Concept (PoC) to transition customer communication channels from Salesforce and Striata to AWS Simple Email Service (SES), followed by executing the full production migration.
  • High-Throughput Composition Engine: Architect and build a scalable message composition engine capable of real-time message assembly and dispatch at throughputs exceeding 750 TPS (transactions per second).
  • Referral System Integration (PoC): Lead the research, prototyping, and Proof of Concept for integrating a dedicated third-party or proprietary "Refer-a-Friend" platform into the existing ecosystem.
  • Analytics & Dashboard Modernization: Audit, redesign, and migrate existing operational and analytical reporting dashboards to a modern, unified data visualization platform.

Software Engineering Manager

Apr 2024 - Jan 2025
AI4Banking
  • Internal Knowledge Assistant: Developed a custom Microsoft Teams plug-in enabling employees to query enterprise documents via an AI interface for rapid information retrieval.
  • Prompt Management Interface: Built a front-end application allowing staff to create, save, and deploy custom user prompts as reusable system instructions to automate and streamline daily banking workflows.
  • Fraud Simulation & Training PoC: Engineered an interactive role-playing Proof of Concept to train and assess customer support agents against emerging fraud scenarios, featuring an end-to-end voice-to-text / text-to-voice bridge alongside automated post-session performance evaluations.

Software Engineering Manager

Nov 2022 - Apr 2024
Chatbot | Content Editor
  • Developed and maintained the Chatbot squad's React/Node.js tooling, improving UI/UX for the content creation team.
  • Migrated Global Pay Outbound to LoopBack 4 and adapted it to the RippleNet blockchain payments network.
  • Integrated MongoDB with MicroStrategy, enhancing fraud, financial-monitoring, and compliance reporting.
  • Supported production platform migrations and resolved live production incidents.

Software Engineer - Consultant Grade 3

May 2021 - Nov 2022
Chatbot | Content Editor
  • Modernized chatbot content infrastructure: maintained full-stack React/Node.js applications, introducing reusable UI components and robust API integrations to enhance platform stability.
  • Streamlined content operations by modernizing the Chatbot squad's React/Node.js tooling, significantly reducing manual authoring overhead through UX enhancements.
  • Accelerated content authoring cycles by redesigning core React/Node.js tooling for the Chatbot squad, eliminating operational bottlenecks for non-technical stakeholders.
  • Partnered with content teams to iteratively refine internal tools (React/Node.js), conducting user feedback loops to deliver intuitive, high-efficiency editorial interfaces.

Software Engineer - Consultant Grade 2

Oct 2018 - May 2021
OnePayFX
  • Architected RippleNet blockchain integration: migrated the Global Pay Outbound platform to LoopBack 4, enabling secure, low-latency settlement on distributed ledger infrastructure.
  • Engineered MongoDB & MicroStrategy data pipelines to power mission-critical reporting for enterprise fraud detection, AML/financial monitoring, and regulatory compliance.
  • Guaranteed 24/7 system reliability: orchestrated high-stakes production platform migrations and served as primary on-call for triaging, resolving, and conducting RCAs for critical live incidents.

Makers Academy

United Kingdom

Junior Software Engineer

May 2018 – Oct 2018
Contractor to Santander Global Pay Outbound
  • Drove core Node.js backend development for Global Pay Outbound, rolling out high-priority features while refactoring legacy codebases to systematically eliminate technical debt.

Pisani Plc

United Kingdom

IT & Operations Manager

Feb 2011 – Jun 2017
  • Drove business transformation initiatives, establishing modernized operating frameworks that accelerated process velocity by 30%.
  • Directed IT infrastructure restructuring and successful rollout of an integrated ERP/CRM solution, generating £50k+ in recurring annual cost savings.

Systems Sunlight S.A.

Greece

Product Manager — Supply Chain & Operations

Oct 2008 – Dec 2010
  • Directed end-to-end product lifecycle management for UPS systems, telecom power supplies, and industrial battery chargers, cultivating key strategic partnerships to expand market footprint.

G.M.M. S.A. Larco

Greece

Technical Analyst / Project Manager

Sep 2006 – Oct 2008
  • Streamlined operational workflows by analyzing and optimizing critical processing procedures, while spearheading strategic procurement tenders for high-spec facility and laboratory equipment.

Education

Full-Stack Web Development Bootcamp
Makers Academy — TDD, OOP, pair programming, MVC/DDD, Agile/XP
2017 – 2018
PhD, Chemical Engineering
Imperial College London — "Combining Ionic Liquids and Supercritical Fluids for Clean Technology"; 4 peer-reviewed publications
2001 – 2004
MSc, Advanced Chemical Engineering
Imperial College London
2000 – 2001
BEng (Hons), Chemical Engineering
London South Bank University
1997 – 2000

Contact

Interested in working together, or just want to talk tech?

Email LinkedIn GitHub