Y·L

Available for contracts

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digital products, internal tools and AI systems expertly delivered

I’mYohannes,aseniorsoftwareengineerwhocraftscustomer-facingproducts,internalplatforms/toolsandAIsystemsforstartupsandenterprises.

Explore servicesView featured work
11+
Years building production systems
3
Cloud platforms: AWS, Azure and GCP
10
Completed projects

How I can help

I design, build and improve production software for startups and product teams, from full-stack web and mobile applications to AI integrations.

Available for fixed-scope delivery, embedded contracts and technical rescue work.

Full-stack product delivery

Build or extend production-ready web and mobile products, from discovery and architecture through launch and handover.

  • MVPs and product features
  • Accessible interfaces and design systems
  • Web and cross-platform mobile delivery

AI features and automation

Add useful AI to products and workflows, with the safeguards needed to move beyond a fragile demonstration.

  • AI discovery and working prototypes
  • Agents, RAG and knowledge search
  • Evaluation, guardrails and human approval flows

APIs, cloud and integrations

Connect products to the services and data they rely on, then deploy them on maintainable cloud infrastructure.

  • REST, GraphQL, gRPC and WebSocket APIs
  • System and data integrations
  • Microservices, infrastructure as code and CI/CD

Modernisation and technical leadership

Stabilise existing products, remove delivery bottlenecks and leave teams with maintainable software.

  • Architecture and code audits
  • Testing, reliability and performance improvements
  • Embedded leadership, mentoring and handover

Working stack

Core

  • TypeScript
  • React / Next.js
  • React Native / Expo
  • NestJS / Fastify / Hono
  • Node.js
  • Python
  • Go
  • PostgreSQL
  • MySQL
  • SQLServer
  • MongoDB
  • Redis
  • AWS / Azure / GCP
  • Docker
  • Terraform

Applied AI

  • LangGraph
  • Qdrant
  • Mem0
  • Vertex AI
  • OpenAI API
  • Claude API

Selected clients

Featured work

Sky Mobile

  • E-commerce
  • Full-stack engineering
  • Performance
Current Sky Mobile storefront
Current Sky Mobile product page
Current Sky Mobile checkout plan page
Current Sky Mobile checkout page

Worked across a React server-rendered storefront, GraphQL APIs and Node.js microservices for Sky Mobile. Used production observability to diagnose performance bottlenecks and errors, then shipped incremental, A/B-tested improvements.

Outcomes

  • Performance and stability work helped reduce error rates by 70%.
  • Together with A/B-tested frontend improvements, the work supported an 8% sales increase.
Role
Senior Software Engineer
Built with
  • TypeScript
  • React
  • Node.js
  • GraphQL
  • Apollo
  • XState
  • Optimizely
  • Dynatrace
  • Grafana
  • Kibana
  • Kafka
Visit Sky Mobile (opens in a new tab)

SES Global

  • Enterprise portal
  • Backend architecture
  • Full-stack
  • Cloud delivery
SES
Client work · visual withheld

Architected and delivered backend and full-stack capabilities for a unified customer portal serving enterprise and government customers. Built Azure-hosted Node.js microservices and integrated enterprise data sources and APIs.

Outcomes

  • Built various full-stack product features.
  • Built email, export, audit-log and notification services.
  • Engineered the email service for capacity in the millions of requests per day.
  • Managed infrastructure changes with Terraform.
Role
Senior Software Engineer
Built with
  • TypeScript
  • React
  • Node.js
  • Fastify
  • Prisma
  • SQL Server
  • SAP HANA
  • InfluxDB
  • Redis
  • Azure
  • Terraform
Visit SES (opens in a new tab)

Klekt Marketplace

  • E-commerce
  • Greenfield delivery
  • Testing and CI/CD
Current Klekt marketplace homepage with navigation, campaign artwork and product discovery
Current Klekt product catalogue with category filters and a grid of authenticated footwear

Built product, search and seller-account experiences for a greenfield marketplace using server-rendered Next.js. Developed GraphQL APIs and middleware, evaluated technology choices and mentored engineers.

Outcomes

  • Established unit, integration and end-to-end testing alongside CI/CD.
  • Delivered across product discovery, search and seller-account journeys.
Role
Senior Software Engineer
Built with
  • TypeScript
  • Next.js
  • NestJS
  • Apollo GraphQL
  • Vendure
  • Jest
  • Cypress
  • Redis
  • Vercel
  • GCP
  • Terraform
Visit Klekt (opens in a new tab)

Mode Banking

  • Fintech
  • Backend modernisation
  • Cloud architecture
Archived Mode Banking homepage section introducing its money and Bitcoin mobile app
Archived Mode Banking product section showing a Bitcoin account and transaction interface

Migrated a Koa.js and MongoDB monolith towards an AWS microservice architecture, built customer and merchant onboarding APIs in NestJS, and implemented OAuth 2.0 authentication aligned with RFC 6749.

Outcomes

  • Integrated onboarding services with AWS ECS, KMS, RDS, Cognito, API Gateway, SQS and SNS.
  • Streamlined CI tasks to improve build speed, developer productivity and operating cost.
Role
Senior Backend Engineer
Built with
  • TypeScript
  • NestJS
  • Koa.js
  • MongoDB
  • PostgreSQL
  • OAuth 2.0
  • REST
  • CQRS
  • Docker
  • Terraform
  • AWS

Deloitte FinTech

  • Fintech
  • Full-stack delivery
  • Cloud infrastructure
Deloitte
Client work · visual withheld

Built a multi-tenant, cloud-native SaaS for a fintech AML/KYC solution, integrating React frontends with NestJS microservices and blockchain-based identity technology.

Outcomes

  • Developed the fullstack app.
  • Built the CI/CD pipeline and AWS infrastructure for APIs, access control and service delivery.
  • Shipped to production and used by well known banking clients.
Role
Full-stack Software Engineer
Built with
  • TypeScript
  • React
  • Redux
  • NestJS
  • TypeORM
  • WebSockets
  • Docker
  • MySQL
  • AWS
  • CloudFormation

Digital Detox

  • Agency delivery
  • Technical consultancy
  • Web and mobile
Digital Detox project collage showing mobile and web interface work
Digital Detox website view presenting its product-delivery work

Delivered web and mobile products across cryptocurrency, telecoms, IoT and education. Work included serverless APIs, React applications, a unified frontend framework and mobile delivery.

Role
Full-stack Software Engineer
Built with
  • JavaScript
  • React
  • React Native
  • Redux
  • Node.js
  • Next.js
  • Jest
  • Storybook
  • Expo
  • AWS Lambda

LBX Mobile App

  • Cryptocurrency
  • Cross-platform mobile
  • Full-stack delivery
LBX exchange interface showing account balances and cryptocurrency prices
LBX mobile wallet interface on an iPhone

Built a cross-platform exchange and wallet application alongside a full-stack registration and KYC web flow for London Blockchain Exchange.

Outcome

  • Delivered feature development, code review, maintenance, builds and deployments.
Role
Full-stack Software Engineer via Digital Detox
Built with
  • React Native
  • React
  • Redux Saga
  • Node.js
  • Next.js
  • Jest
  • Expo
  • Sentry

FSB Technology

  • SaaS platform
  • Frontend leadership
  • Performance
FSB back-office dashboard showing account and operational controls
FSB SaaS interface showing detailed operational data

Led frontend delivery for a multi-tenant back-office SaaS platform and contributed to customer-facing white-label applications for global clients.

Outcomes

  • Built 40 bespoke back-office applications across sportsbook, CRM, CMS, analytics, site management and operations.
  • Built customer facing web app and managed deployements for 15+ global clients.
  • Caching reduced XHR requests by 40%.
Role
Frontend Software Engineer; Lead Frontend, 2016–2017
Built with
  • JavaScript
  • ExtJS
  • Node.js
  • Express
  • Jasmine
  • Nightwatch
  • Docker
  • Bash
  • Ant
  • Jenkins

Have a project that needs shipping?

Bring me in for a focused build, an embedded contract or a technical rescue.

Book a 15-minute call