Hi, I'm William Onsare
I have 5+ years of experience building production web applications, with hands-on experience across software engineering, conversational AI, prompt engineering, APIs, product UX, and digital product delivery.
About Me
I'm a Software Engineer with 5+ years of experience building and improving production digital products.
My foundation is in React, TypeScript, APIs, and modern web engineering, but my work has increasingly expanded into AI-powered systems, conversational interfaces, product workflows, and operational tooling.
At ChatSasa, I've contributed to an AI-assisted omnichannel customer-support platform spanning WhatsApp, SMS, email and web chat. My work has included AI integrations, prompt and context design, human-in-the-loop workflows, message classification, routing, dashboards, APIs and agent-facing experiences.
I enjoy working where technology, users and business problems intersect - taking ambiguous requirements, understanding the underlying problem, building practical solutions, and iterating based on real-world feedback.
Technical Expertise
React, TypeScript, Next.js, modern state management, and scalable UI architecture.
Collaborative Delivery
Strong cross-functional collaboration with product, design, and backend teams.
User-Focused Interfaces
Building intuitive, accessible, and performance-conscious user experiences.
AI Product Integration
Hands-on experience integrating AI-powered features into production SaaS products.
Skills & Expertise
AI & Conversational Systems
- OpenAI API integrations
- Prompt engineering
- Context design
- Structured outputs
- Intent classification
- Tool/function calling
- Guardrails
- Human-in-the-loop workflows
Software Engineering
- React
- TypeScript
- Next.js
- REST APIs
- GraphQL
- PostgreSQL
- Component architecture
- State management
- Production frontend systems
Product & UX
- User flows
- Product requirements
- Prototyping
- Interface design
- Usability
- Stakeholder collaboration
- Translating business requirements into practical digital experiences
Integrations & Delivery
- API integrations
- Messaging platforms
- Testing
- CI/CD
- Debugging
- Technical documentation
- Production troubleshooting
Education & Languages
Education
Bachelor's Degree in Applied Computer Science
Chuka University
2015 - 2019
Languages
How I Work
Engineering Depth
I care about maintainable systems, predictable behaviour and production reliability.
AI Experimentation
I explore where AI can meaningfully improve workflows rather than adding AI simply because it is available.
Product Thinking
I focus on the underlying problem, user behaviour, trade-offs and measurable outcomes — not just implementation.
Operational Ownership
I understand that successful products extend beyond code. They require prioritisation, customer feedback, communication, coordination and continuous improvement.
Featured Projects
Production apps demonstrating software engineering, AI workflows, and product thinking
ChatSasa - Smart Inbox
AI-Powered Omni-Channel Customer Support Platform
Problem
Businesses struggle with fragmented customer messages across channels (WhatsApp, email, SMS, socials), slow response times, and no unified analytics to prioritise high-value tickets.
My Role
Lead frontend developer: designed and implemented the product UI, built responsive interactive components, integrated analytics visualisations, and delivered the smart-inbox flows used by support agents.
Tech Stack
Impact
- Consolidated multi-channel conversations into a single inbox, increasing agent throughput
- Reduced average response and resolution times through prioritised queues and task assignment
- Delivered dashboard analytics that inform daily ops and surface performance trends
User-friendly inbox, fast-loading analytics, frictionless CTAs for onboarding & trial conversions.
Conversational AI Prompt Lab
Practical Prompt Engineering & LLM Workflows
Problem
A public engineering portfolio exploring how prompts and LLM workflows can be designed, evaluated and improved for production-oriented applications.
My Role
Explores prompt architecture, structured outputs, intent classification, guardrails, human escalation, evaluation, versioning, reliability, and cost & latency considerations.
Tech Stack
Impact
- Public engineering portfolio demonstrating practical AI workflow design
- Exploration of production-oriented prompt architecture and evaluation
- Documentation of reliability, cost, and latency considerations
Prompt architecture · Structured outputs · Intent classification · Guardrails · Human escalation · Evaluation · Versioning · Reliability · Cost & latency considerations
SMSLeopard Broadcast Platform
Communication / SaaS
Problem
Businesses needed a dependable way to run large-scale SMS & WhatsApp broadcast campaigns, and integrate messaging into existing systems without losing deliverability or developer ergonomics.
My Role
Frontend contributor working with a team of senior engineers - I implemented recent features, wired frontend components to APIs, improved developer-facing docs/examples, and assisted with QA and performance tuning.
Tech Stack
Impact
- Reduced campaign setup time through a streamlined broadcast composer and templates
- Enabled external integrations via developer APIs, making it easier for clients to automate messaging workflows
- Improved dashboard visibility and analytics so operations could monitor campaign health and troubleshoot faster
API integration hooks, dashboard analytics, testing, documentation, and release coordination.
M-Pesa Hash Decoder
Developer Tool / Payments Utility
Problem
Kenyan businesses and support teams needed a fast, reliable way to decode and verify M-Pesa/Paybill transaction hashes to troubleshoot payments and reconcile records.
My Role
Solo frontend implementation: designed UI, implemented API integration, added copy/paste-friendly workflows.
Tech Stack
Impact
- Reduced time-to-verify M-Pesa transactions from 20+ minutes to under 2 minutes
- Improved reconciliation accuracy for finance teams and reduced support ticket volume
- Adopted by small merchants for quick on-the-spot verification during customer disputes
Clear onboarding, clean UX for parsing data, copy/clipboard flow.
PodoaPlus
Marketplace - Beauty & Wellness Prototype
Problem
Local beauty professionals lacked a trustworthy, discoverable channel to attract clients and manage bookings efficiently.
My Role
Lead frontend / UX: designed landing and search-first discovery UI, implemented booking & provider signup flows, integrated reviews/testimonials and responsive layouts.
Tech Stack
Impact
- Lowered discovery friction — users find relevant pros via service + location search in one step
- Streamlined business onboarding and service listings for local professionals
- Improved conversion with clear pricing, social proof and an easy booking flow
Progressive enhancement, navigation persistence, mobile-optimized flow.
Entrepreneurship
Coolato Creamies
Founder & Operator
I co-founded and operate a customer-facing dessert business, gaining hands-on experience across product decisions, pricing, customer experience, supplier coordination, operations, problem-solving and continuous improvement.
This experience has strengthened my understanding of ownership, resource constraints, customer needs and the realities of turning ideas into sustainable operating systems.
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Let's Connect
Open to opportunities, let's discuss how I can contribute to your team