
Tunmise Fatunmbi
Verified Expert in Engineering
Systems Engineer and Developer
Tokyo, Japan
Toptal member since June 20, 2025
Tunmise has over five years of experience as a systems engineer. He has worked in front-end, back-end, and full-stack roles across a diverse range of industries, from small startups to large, established companies. This extensive experience has broadened Tunmise's perspective and equipped him with the skills to tackle a wide array of software-related challenges.
Portfolio
Experience
- System Design - 5 years
- Next.js - 5 years
- Laravel - 4 years
- PostgreSQL - 4 years
- Flutter - 4 years
- Jest - 3 years
- Svelte - 3 years
- Nuxt.js - 2 years
Work Experience
Software Engineer
Woven
- Architected large-file upload infrastructure to S3 (presigned URLs, chunked/resumable transfers) with fault-tolerant client-side persistence (Uppy and IndexedDB) surviving browser crashes and multi-tab sessions.
- Developed core platform services on React/Python BFF architectures with OAuth2/OIDC (Keycloak) and compliance-driven access control across product teams.
- Contributed to the building of the Integrated Experience of Woven by Toyota's digital-twin platform.
- Contributed to an AWS Bedrock (AgentCore) multi-agent workstream: agent runtime and memory, API-to-tool gateways, orchestration, and identity/observability.
Senior Full-stack Engineer
Mico Inc
- Owned LINE message delivery: a permanent retry fix that stops dead 400/409 sends from looping and burning quota, plus a CloudWatch and RDS delivery-monitor Lambda that surfaces failures the team used to miss.
- Rolled out the Catch All webtag loader (auto-tracks a site with no manual tag edit, per-site gated, 304 caching) and split the prospect flag to separate tracking from UI visibility.
- Built a self-contained LINE API mock server so the team can develop against LINE without touching the real sandbox.
- Rebuilt catalog search from 6 fields to a full pg_bigm index, and diagnosed a full-scan that pushed Aurora to 63% CPU and 74-second responses on a 125k-row tenant.
- Worked full-stack on Mico Marketing Cloud, a multi-tenant, event-driven LINE marketing and CRM SaaS on AWS (NestJS, Next.js, Kafka/Kinesis/SQS, MySQL/Aurora/TiDB/DynamoDB, Terraform).
Software Engineer
ZeroSpec
- Collaborated with a 10-person engineering team to build an IoT-powered SaaS platform for gas delivery companies, enabling real-time kerosene tank monitoring and smart delivery scheduling.
- Developed core parts of the business dashboard using TypeScript, Svelte, TailwindCSS, XState, and Hono, focused on customer management, tank status, and delivery automation.
- Designed and implemented atomic UI components for the v2 dashboard release, improving design consistency and component reusability.
- Contributed to back-end services by fixing bugs and building new features such as car fleet management, receipt tracking, and service-level permissions, using PostgreSQL and TypeORM.
- Conducted frequent pair code reviews on GitHub and AWS CodeCommit, promoting code quality and knowledge sharing across the team.
- Optimized multiple services by redesigning database queries, reducing response time by 33%, and significantly improving performance in production.
- Maintained product quality by writing comprehensive unit and end-to-end tests in Jest, reducing regression bugs, and supporting continuous delivery.
Software Consultant
Tippsy
- Translated Figma designs into pixel-perfect, responsive web components using Next.js, ensuring design fidelity across multiple devices.
- Worked with complex integrations including LoyaltyLions, Stripe, Reviews.io, Klaviyo, and Shopify API in a custom Shopify Hydrogen and Next.js storefront.
- Maintained and debugged NestJS back-end systems, addressing Shopify API versioning and evolving business rules with continuous uptime.
- Revamped shipping logic for the largest Japanese sake brand in the US ($12+ million in annual revenue), reducing support tickets by 39% and cutting order rejections by 22%.
- Collaborated closely with UI/UX designers to launch a Japanese snack eCommerce platform, resulting in a 28% increase in revenue due to improved user experience.
- Developed branded initiatives such as sake clubs, integrating them into the site architecture to streamline subscriptions and elevate the brand's customer experience.
Senior Software Engineer
Booost
- Resolved critical bugs and implemented new features across key modules, including global warming and energy conservation reporting, supply point processing, and product separation, using Laravel (PHP) and Vue.
- Wrote comprehensive unit tests with Pest PHP to ensure test coverage and robustness across core services.
- Led the development of an LLM-powered translation tool, improving contextual understanding and UX for multilingual users across the product suite.
- Headed ideation and UI/UX redesign and front-end development of a new conceptual ERP version using Vue/Nuxt and Vuex, which could lead to a 60% reduction in customer onboarding time, improving usability and accelerating adoption.
- Improved ERP Carbon Measurement API speed by 600% by re-architecting the query strategy and optimizing MySQL and Laravel Eloquent, dramatically reducing load time.
Front-end Developer
Fourdigit
- Served as a bridge between design and engineering, converting design prototypes and interaction models into production-level React components.
- Engaged directly with clients in technical discussions to translate UX concepts into feasible development strategies.
- Integrated motion design and microinteractions using tools like Framer Motion or GSAP to enhance visual storytelling and engagement.
- Contributed to DX initiatives, improving internal workflows with reusable front-end templates and shared utilities.
- Collaborated with back-end developers to design RESTful API integrations, data flows, and real-time UI updates.
- Participated in client workshops and design sprints, contributing technical insights and feasibility assessments during early project phases.
- Delivered front-end solutions for enterprise and global brand clients, adhering to FOURDIGIT’s design and accessibility standards.
- Collaborated closely with designers and product strategists to iterate on UX flows, applying user feedback and analytics to improve usability.
Technical Lead
CLB
- With a team of 3, developed a complete development cycle of a new restaurant delivery system.
- Implemented 3rd-party APIs such as payment gateways and integrated IoT devices, driving vendor adoption up by 33%.
- Developed a mobile admin app in Flutter and Dart, reducing user cognitive load by 70%, which enhanced ease of use.
- Improved code quality through rigorous code reviews, unit testing, and automated CI/CD deployment with GitHub Actions.
- Selected technologies and led the development of API endpoints in PHP, achieving sub-100ms response times.
Project History
Ontomorph
http://ontomorph.comI designed its web applications and TypeScript and Python services, including clinical terminology, identity and consent, lab interpretation, simulation, and genomics components.
The platform includes auditable probabilistic record matching and a clinical scoring engine based on published NEWS2 criteria.
I built the system around explicit service boundaries, PostgreSQL-backed models, provenance, and validation because medical data needs traceable decisions.
I also implemented an MCP tool layer for code validation, terminology translation, drug facts, interactions, reference ranges, clinical decision support, medication deduplication, and unit conversion.
Fleet Reinforcement Learning Environment Development
• Built high-fidelity simulation environments for enterprise software, enabling leading AI labs to train computer-use agents on realistic, interactive workflows.
• Developed pixel-accurate replicas of complex applications such as Zillow and Google Maps using Svelte, TypeScript, and a lightweight full-stack architecture optimized for performance.
• Leveraged AI-assisted development (Claude Code and Cursor) to orchestrate multi-agent workflows, accelerating environment creation and improving UX precision.
• Collaborated with global teams of researchers and engineers to refine UX consistency, simulate real-world data interactions, and ensure scalability across diverse training environments.
Owanbe Japan
http://owanbe.jpI designed the ticketing core so that per-seat tickets are HMAC-signed and issued transactionally on the Stripe payment webhook, minting a valid ticket only once payment settles, with separate paid, promotional, and complimentary tiers.
I built on-site check-in as a dedicated door scanner that verifies the signed QR tickets at the gate, backed by digital wallet passes for attendees.
I hardened the admin surface with passwordless magic-link authentication and an append-only audit log that records every privileged action.
I built a custom signal-processed talking-drum (gangan) web-audio engine as the brand's signature sound.
MyBenkio
http://mybenkio.comI designed and built it from greenfield across Next.js, React, TypeScript, Tailwind, and PostgreSQL, and it was launched in January 2026.
Students across universities use it for AI explanations and visual aids, seven quiz formats, spaced-repetition flashcards, study recommendations based on exams and weak concepts, progress statistics, streaks, and leaderboards.
I also built a quality gate that checks generated questions with deterministic heuristics before an LLM judge and fails closed on malformed output.
I owned the product model, relational schema, APIs, AI workflows, and learner experience.
Blessed to Be a Blessing Gifting Platform Inc
https://b2bgiftingplatform.com/I designed a capability-based access-control system with a capability catalog, a precedence resolver, and per-community moderation scopes, where privilege changes run through Postgres RPCs paired with an audit log.
I hardened authentication for production with TOTP two-factor and backup codes, email verification, session-epoch invalidation on credential changes, database-backed rate limiting on login and 2FA, and a custom-token password reset flow.
I built the payments layer with a provider-agnostic gateway over Stripe, a cron worker for scheduled transfers, atomic wallet operations that removed transfer race conditions, admin-reviewed withdrawals, and CSV and PDF statement export.
I delivered real-time community chat with moderator mute and soft-delete, a preference-gated notification system with event-reminder and weekly-digest crons, and an SEO stack of an MDX blog, JSON-LD, and sitemap/robots routes.
Villager Square Dating Ecosystem
http://villagersquare.com• Architected and developed cross-platform mobile applications using Flutter, implementing secure authentication, real-time interactions, and scalable back-end integrations.
• Incorporated findings from psychology and evolutionary biology to design algorithmic guardrails that promote intentional, meaningful user engagement.
• Built and led a multidisciplinary marketing and product team, overseeing go-to-market strategy, growth experiments, and early traction initiatives.
Mona Clinic: AI Agent Integration in Customer Support Flow
• Built a centralized knowledge base for internal documentation, enabling real-time access and updates for AI responses via staff-editable content.
• Implemented LINE Messaging API webhooks to intercept and respond to messages, ensuring accurate, human-reviewed replies in critical interactions.
• Developed a custom business dashboard using Next.js, tailored to operational and analytics needs with real-time filtering, response monitoring, and administrative controls.
• Built Shopify data access via GraphQL to the agent, facilitating inventory sync, order tracking, and real-time customer data flow for improved eCommerce performance.
• Engineered a customer retention pipeline, enabling segmented lifecycle communication based on behavioral triggers to improve patient follow-up and engagement.
• Applied advanced prompt engineering to handle complex and ambiguous scenarios, ensuring accurate, expected outcomes across various use cases.
Lerxs Health
http://lerxs.com• Designed and implemented a platform dashboard using Next.js, TypeScript, and PostgreSQL, and handled real-time communication using WebRTC.
• Launched a mobile version on Flutter, successfully deployed on Google Play and iOS stores, expanding accessibility.
• Built and led a dynamic team of 10, fostering innovation across various product aspects.
Haards Platform: Decentralized DOOH Advertising
https://haards.com• Built the platform dashboard with Next.js/TypeScript, PostgreSQL, and real-time communication using websockets.
• Built the client app on Flutter and deployed it on the Google Play Store
• Built a growing team of five working on various aspects of the product.
SC Vision: Digital Signage System
https://www.soft-creation.co.jp/• Built the admin dashboard using Flutter (Dart), implementing real-time screen control, content previews, and custom scheduling via Socket.IO.
• Developed back-end infrastructure using Appwrite for authentication, file storage (video, HTML, Adobe Animate), and NoSQL data management.
• Architected and built the client application using Electron/JavaScript, enabling real-time sync with the admin dashboard and schedule-based playback.
• Implemented robust client authentication, scheduling workflows, and content sync logic with support for Adobe Animate, MP4, PNG, and HTML assets.
• Designed and deployed a Node.js/Express.js back-end server handling CI/CD, WebSocket events, and Adobe Animate rendering logic. Deployed the system on Google Cloud Platform (GCP), leveraging cloud infrastructure for scalability, resilience, and real-time performance.
BingoHub
https://bingohub.io/Education
Bachelor's Degree in Electrical Control and Systems Engineering
Hokkaido University - Hokkaido, Japan
Diploma in Japanese Language and Culture
Osaka University - Osaka, Japan
Skills
Libraries/APIs
React, Vue, jQuery, Stripe API, Node.js, Stripe, REST APIs, GetX, API Development, OpenAI API, Object Windows Library (OWL), GraphQL API, WebGL, Shopify API, Socket.IO, Three.js
Tools
Figma, Git, AI Prompts, Claude, Shadcn, Claude Code, Firebase Authentication, Codex, Prisma, Auth0, GraphRAG, MATLAB, Builder.io, GitHub, Amazon Simple Queue Service (SQS), Amazon Elastic Container Service (ECS), Keycloak, Amazon Cognito, Terraform
Languages
Python, PHP, TypeScript, Dart, JavaScript, CSS, OWL, Kotlin, HTML, HTML5, CSS3, GraphQL, SPARQL, Shapes Constraint Language (SHACL), RDF, Java, R
Frameworks
Next.js, Laravel, Flutter, Electron, Svelte, Jest, Tailwind CSS, Redux, React Native, Fastify, Nuxt.js, JSON Web Tokens (JWT), .NET, Ontology Framework, Agentic Frameworks, NestJS
Paradigms
E2E Testing, Desktop App Development, Database Design, Mobile Development, Unit Testing, REST, Role-based Access Control (RBAC), DevOps, HL7 FHIR Standard, Microservices Architecture, Microservices, Web Architecture, Model Context Protocol (MCP)
Platforms
Shopify, MacOS, Firebase, Docker, Android, Linux, AWS IoT, Amazon Web Services (AWS), iOS, AWS Lambda, Desktop, Google Cloud Platform (GCP), Harness, Android TV, Ollama, Algolia, Klaviyo, Azure, LiveKit, Windows
Storage
PostgreSQL, MySQL, NoSQL, Database Structure, Amazon S3 (AWS S3), JSON, Amazon DynamoDB, MongoDB, Redis, SQLite
Other
Machine Learning, APIs, Large Language Models (LLMs), WebSockets, Bun, Mobile App Development, Mobile Apps, API Integration, Front-end Development, Full-stack, Supabase, SaaS, Software Architecture, Prompt Engineering, Integration, Front-end, Back-end, Web Development, Minimum Viable Product (MVP), Startups, User Experience (UX), Product Owner, Product Ownership, User Interface (UI), Data Visualization, Dashboards, Zustand, AI Integration, Vite, Back-end Development, User Roles, Cloud, Data Modeling, Generative Artificial Intelligence (GenAI), Scalability, Scalable Architecture, LLM Integration, RAG Systems, AI-assisted Development, Mobile App Security, FastAPI, Authentication, Webhooks, Ontologies, Knowledge Graphs, Architecture, Data Governance, Enterprise Architecture, Multi-tenant Architecture, Data Security, Agentic Coding, Documentation, Workflows, Identity Verification, Push Notifications, Application State Management, Mobile Architecture, Offline Data Synchronization, Data Engineering, CI/CD Pipelines, Loyalty Programs, SvelteKit, XState, Maps, Artificial Intelligence (AI), AI Agents, Full-stack Development, CTO, Solution Architecture, AI Tools, AI Automation, OpenAI, Meta Ads, Videos, Security, Project Consultancy, Desktop App, OAuth, OpenID Connect (OIDC), Cryptography, HIPAA, Taxonomy, Financial Data, LLM Agents, AI Agent Orchestration, Agentic AI, Plugins, Technical Leadership, Android TV Wrapper, Audio Streaming, Streaming, Video Streaming, Data Analysis, Research, System Design, Control Systems, Electrical Engineering, Japanese, Social Impact, Open-source LLMs, TypeORM, Apple Pay, Cursor AI, Amazon RDS, LINE Bots, Deliverability, Argo Workflows, Argo CD, Payments, Workers, Edtech Design, Education Technology (Edtech), Compliance
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