Adilson M. Bacelar

Slice Mobile, London, UK — UK eSIM provider (MVNO) offering 5G data, loyalty rewards such as cashback, and community features like data gifting and groups

• –Built and shipped an MCP (Model Context Protocol) server (NestJS, official TypeScript MCP SDK over Streamable HTTP) exposing Slice account data — plan, balance, EU roaming, billing, promos, and add-ons — to AI assistants (Claude, ChatGPT) as six typed, schema-validated tools, with per-user rotatable bearer-token auth, per-call audit logging (PII-redacted in production), and graceful degradation across four upstream microservices.
• –Deliberately scoped the MCP server to read-only — returning authenticated in-app deeplinks for payment and other irreversible actions instead of executing them — so an AI agent can surface account insights while billing changes always require explicit, in-app user confirmation.
• –Designed, built, and shipped the data-gifting platform end-to-end across backend and mobile (NestJS, React Native) as the originating engineer, owning the full telecom-backed flow (validate, deduct, create subscription, persist) with graceful degradation on upstream failures.
• –Built the recommendation service powering suggested contacts and subscription-aware gifting, blending telecom data with in-app behavioural signals (gift events, group membership) and failing closed when dependent services are unavailable to avoid surfacing stale or partial data.
• –Contributed reusable NestJS modules to the shared internal library — originating the data-gifting client and acting as primary developer of the telecom (Mindszi) client over mTLS, with balance/roaming typing, fail-closed behaviour, and a mock test harness — reducing boilerplate across services.
• –Designed a clock-driven, multi-tier configuration fallback (remote config to on-device cache to hardcoded defaults) so the mobile app degrades gracefully and stays functional when the centralised feature-flag service is unreachable.
• –Refactored onboarding flows to increase user agency and clarity, resulting in a 22% increase in completed onboarding sessions within one month of release.
• –Reduced checkout instability through cart deduplication and reliability improvements.
• –Embedded observability (Sentry, Better Stack, Prometheus) and CI/CD pipelines (GitHub Actions, OpenAPI schema publishing, Snyk scanning) for services deployed to Kubernetes via Helm and ArgoCD, improving deployment confidence and production visibility.

Searchland, London, UK — all-in-one UK property and planning data platform

• –Replaced a complex Temporal-based asynchronous setup with BullMQ-driven background processing, reducing task failure rates from 35% to 7%, with automated retries stabilising import and report workflows.
• –Led backend performance overhaul enabling large-scale geospatial visualisation, reducing response times from seconds to milliseconds and supporting 3,000+ GeoJSON map renders across the UK.
• –Implemented dynamic Level of Detail (LoD) strategies tied to map zoom levels to support high-density geospatial rendering.
• –Spearheaded migration from GraphQL to tRPC, improving type safety, simplifying developer workflows, and enabling fine-grained query-level authorisation.
• –Architected a custom reporting engine generating fully branded PDF and Word reports with fine-grained dataset controls (restrictions, demographics, amenities, historic sales data).
• –Enabled stored sourcing queries to dynamically hydrate reports, allowing users to centre complex spatial filters around specific land titles and include relevant comparable data.
• –Mentored engineers and set architectural standards across backend and frontend systems.

Aviva, London, UK — multinational insurance and pension provider

• –Established coding standards and best practices for React Native and TypeScript, ensuring team adherence to maintain clean, scalable code.
• –Led technical workshops and code reviews, providing mentorship to improve team proficiency.
• –Set technical direction and acted as key decision-maker for technical challenges, aligning solutions with business objectives.
• –Supported sprint planning and delivery, balancing short-term goals with long-term technical health.
• –Maintained application architecture focusing on scalability and performance.
• –Collaborated cross-functionally with API, designers, and technical teams to ensure smooth project delivery.
• –Facilitated onboarding of new engineers and communicated complex technical topics to technical and non-technical stakeholders.

efitter, London, UK — digital shopping assistant aiming to reduce returns due to sizing

• –Led as the sole engineer in a startup, overseeing all aspects of product development.
• –Migrated the core product, a Chrome extension, from vanilla JavaScript (Manifest V2) to TypeScript (Manifest V3) using modern build tools, including Vite.
• –Established a CI/CD pipeline with GitHub Actions for automated testing and deployment to the Chrome Web Store.
• –Developed bespoke internal tools, eliminating the need for costly third-party subscriptions.
• –Currently building B2B offerings using Golang and Docker, powering backends for client-facing dashboards.
• –Implemented logging and analytics systems for performance monitoring using the ELK Stack (Elasticsearch, Logstash, Kibana).

Wellcome Trust, London, UK — museum and library centred on medicine research

• –Developed developer-focused tools to enhance workflows within Yarn workspace monorepos.
• –Improved collection discoverability by implementing global search and restructuring the search hub to increase user affordance.
• –Managed and enhanced a mission-critical backend API, optimising Elasticsearch to ensure reliability and performance.
• –Implemented AI-powered media transcription with speaker identification, enhancing search precision and user experience for research purposes.

Adarga, London, UK — AI powered Research and Analysis SaaS company

• –Containerised and integrated React and TypeScript micro-UI components into a robust CI/CD pipeline using Docker and GCP, ensuring efficient testing and continuous deployment of web applications using micro-frontend architecture.
• –Implemented optimised GraphQL endpoints for data retrieval in the second version of the application.
• –Implemented a user interface that allowed for the handling of large and ever moving datasets, with a focus on performance and scalability.
• –Implemented a user interface that properly emphasised the powers of natural language processing (NLP), machine learning (ML) and graph databases to provide a more accurate and relevant search experience.

TELUS Health (Formerly LifeWorks), London, UK — HR services and technology SaaS company

• –Led a global team in migrating multiple applications from Angular to ReactJS, ensuring adherence to coding best practices.
• –Contributed to all stages of the SDLC in an agile environment, from design to deployment.
• –Implemented AAA WCAG accessibility standards across client-facing platforms, enhancing usability for individuals with disabilities.
• –Developed a responsive email framework compatible with over 50 languages, increasing international user engagement across all used email clients.
• –Created custom Cookie compliance/GDPR modules to ensure global legal compliance and build customer trust.

Commercial People, London — Residential and Commercial real estate challenger property portal

• –Developed user-friendly and responsive front-end interfaces for mobile and web applications using React and React Native, targeting multiple platforms, including web, iOS, and Android.
• –Created a server-side rendered web app platform with SEO techniques, enhancing the visibility and reach of our products.
• –Engineered a flexible PDF generator in Node.js, enabling efficient creation of lead-generating PDFs with customisable layouts.
• –Led the development and integration of backend services to expand our platform's capabilities, connecting with property providers worldwide for up-to-date property listings.

RIE Studios, London — indie game development studio

• –Founding member of a games company, releasing a game on the Google Play Store.
• –Drove design decisions and meticulously orchestrated player experience in a dynamic, cross-functional team.
• –Coded gameplay mechanics in the Unity game engine using C#, ensuring precise execution.
• –Contributed to a versatile team where adaptability and cross-functional collaboration were paramount.