Portrait of Kelvin John Santos

Hi, my name is

Kelvin John Santos.
Full Stack Software Engineer.

13+ years building high-performance web and mobile applications in fintech and fast-growing startups — scalable SaaS, payments, blockchain, and identity systems. Currently at Bookipi, previously at Xendit (YC S15) and Sleek.

kelvin.js — zsh — 80×10
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01. About

A quick introduction.

I'm a Full Stack Software Engineer with 13+ years of experience building high-performance web and mobile applications in fast-growing startups and fintech environments. My expertise lies in JavaScript/TypeScript (MERN stack), with deep experience in scalable SaaS platforms, payments, blockchain, and identity solutions.

Currently at Bookipi, I drive the development of core products like Invoices and Proposals across web and mobile, working on workflow orchestration with Temporal and cloud infrastructure on AWS — ensuring our systems are secure, reliable, and built to scale.

Beyond coding, I bring a product-focused mindset — aligning technical execution with business outcomes. I've led projects from architecture through deployment and optimization, and I enjoy mentoring peers, identifying product gaps, and pushing continuous improvement.

02. Experience

Where I've worked over the last 13+ years.

Full Stack Engineer · Bookipi

Jun 2024 – Present · Remote

Driving core products — Invoices (web and mobile), Proposals, and more — from feature development through delivery, plus workflow orchestration and cloud infrastructure that's secure, reliable, and built to scale.

MERNReact AWSTemporal

Senior Software Engineer · CodingChiefs (DataChecker.nl)

Jun 2023 – Jun 2024 · Remote

Helped migrate a legacy identity-verification system to a modern stack and built new functionality the old system couldn't support.

GoReact gRPCAI integrations

Architect & Lead Developer · Thinking Active

Jul 2022 – Jun 2023 · Sydney · Remote

Designed system architecture for a blockchain project alongside the CTO — key management, encryption, identity, smart contracts, and cross-chain interoperability.

BlockchainSmart Contracts Security

Senior Staff Software Engineer · Xendit (YC S15)

Jun 2020 – Jun 2022 · Singapore

Built and scaled the invoicing product at one of Southeast Asia's leading payments companies — reliability, security, and architecture for scale.

PaymentsNode.js Full Stack

Senior Software Engineer · Sleek

Dec 2018 – May 2020 · Singapore

Built the platform behind Sleek's company incorporation, corporate secretary, and accounting services — customer app, admin app, and digital document signing.

Vue.jsReact Node.jsMicroservices

Senior Software Engineer · Twist Resources

Aug 2012 – Dec 2018 · Philippines

Researched, designed, and developed features for the company's core products, and trained new hires on the ToolTwist framework.

JavaToolTwist

03. Skills

Technologies I work with day to day.

Languages

JavaScript TypeScript Go Python Java

Frontend

React Vue.js

Backend

Node.js MERN Stack gRPC Temporal

Databases

MongoDB NoSQL RDBMS

Cloud & DevOps

AWS Docker CI/CD

Domains

Fintech Payments Blockchain SaaS

04. Resume

The full picture, in one document.

Want to know more?

Download my resume for the details — and I hope we get to talk soon.

Download Resume