Let's Build Together
I'm a full-stack software engineer with a decade of experience building consumer and enterprise web applications.
I bring startup experience as the first web engineer at an early-stage health tech startup, where I led the development and architecture of clinical web applications until Calm acquired it in 2022.
At Calm, I was part of the Core Platform team and led the design and implementation of multiple business-critical projects.
I collaborate across engineering, product, and design to bring ideas to life. I specialize in building user-friendly, secure, and stable apps. I thrive in a fast-paced environment, constantly gathering insights and improving.
Experience
AI Integrations
Took the initiative to prototype and implement an AI-assisted content system for an extensive content library. Working closely with data scientists, business analysts, and content experts, I implemented a solution that unlocked new insights for the business, improved efficiency for content administrators, and enhanced search and recommendations for end users.
Compliance and Security Expertise
Experienced in highly regulated industries, balancing speed with strict compliance requirements. In one project, I led front-end development for a central account management system, building user-facing and internal applications that met HIPAA standards while adhering to HITRUST security practices. My role involved collaborating across engineering, product, design, and customer experience teams, delivering the project a week early with no critical defects.
Workflow Automation
I transformed a manual, error-prone closed captioning process into an automated workflow, reducing turnaround time from hours/days to minutes. I managed vendor research, prototyping, and stakeholder coordination, building APIs and creating an admin validation UI. This automated system reduced errors and improved accuracy and accessibility.
Analytics
Integrated multiple analytics tools such as Google Analytics, Mixpanel, and Amplitude. Created a central analytics schema and generated client SDKs to establish consistent instrumentation across Web, iOS, and Android platforms.
Testing
Experienced in writing and maintaining unit, component, integration, and e2e tests using Jest, Cypress, and Karate. Devised a testing strategy using analytics, enabling simple implementation and ensuring critical product flows remain functional.
Monitoring and Logging
I've configured monitors and alerts in DataDog and Stackdriver to notify on-call engineers in case of critical system errors. I've also included robust logging and tracing to assist with debugging and establishing an audit trail across microservices.
Internationalization (i18n)
Led a project to support ten languages across various user-facing messaging channels (email, sms, voice, web browser). I set up automation using GitHub Actions and Smartling to ensure translations are always up-to-date.
Accessibility (a11y)
Built and maintained components and pages that comply with WCAG 2.1 AA (Web Content Accessibility Guidelines). I include explicit tests to verify accessibility during development. Familiar with tools such as Axe, Google Lighthouse, and external vendors to perform accessibility audits.
Auth Integrations
I've integrated Auth0 and Okta into multiple Nextjs applications and set up custom claims and permissions to support a secure internal account management tool.
Fullstack Technology
Here are technologies I've used to create both enterprise and consumer applications.
Frontend
- JavaScript
10+ years of experience in JavaScript but prefer TypeScript for most production applications.
- TypeScript
7+ years of experience in TypeScript, bringing a structured, maintainable approach to complex applications.
- React
Experienced in React, favoring hooks and functional components for cleaner, more efficient code.
- Next.js
Extensive experience in Next.js, integrating authentication providers, design systems, monitoring, and analytics.
- Jest
Experienced in Jest for unit and component testing in React.
- Figma
Extensively use Figma to translate design team mocks into products.
- Cypress
Some experience with Cypress for creating integration tests. I have more experience using Karate, a lesser know automation framework.
- Tailwind CSS
Tailwind CSS was used to build this website.
Backend
- Node.js
Skilled in Node.js and its ecosystem (yarn, npm, pnpm), from file management scripts to Express.js APIs and server-side rendering.
- PostgreSQL
Proficient with PostgreSQL, using the pgvector plugin for AI-generated embedding vector operations.
- C#
Experience building REST APIs using C# and ASP.NET.
- OpenAI
Experience integrating with OpenAI APIs for Speech-to-text, Chat Completion, and Text Embedding capabilities.
- AWS
Experience with AWS, using AWS Transcribe for audio transcripts and interacting with S3 for storage.
- Go
Some experience using for Go for building backend APIs along with unit tests.
- Python
Some experience using python for experimenting with AI in Jupyter Notebooks.
Devops
- Terraform
Familiar with Terraform for infrastructure management.
- GitHub Actions
Utilized GitHub Actions for npm publishing, workflow automation, and CI/CD support for web applications.
- Vercel
Frequently use Vercel for hosting personal apps or prototyping; this website is also hosted on Vercel.
- Vault
Experience with Vault for managing secret tokens and API keys.
Recommendations
I worked with Kallen at Rally, Ripple Health Group and Calm. I had the opportunity to work directly day to day during the RHG times and I got to know him better.
Kallen is someone who can deliver in a small or big company; as an engineer he has the key 3 qualities: he delivers with quality and on time, he owns his outcome from implementation all the way to production, he works great with stakeholders.
Kallen is flexible, he wants to deliver value, he is driven by a passion to help the customer and create impact with his work. He is a self starter, has contributed repeatedly in hackathons and spearheaded ambiguous efforts and explorations that pushed him out of his comfort zone in terms of existing knowledge.
He will add value to any company. Please reach out if you need more details.
Anastasios KasiolasCTO @
Calm
I had the pleasure of having Kallen as a direct report, and I can confidently say they are one of the most diligent professionals I've worked with. Every commitment they made was as good as done, with a level of consistency and reliability that set a standard for our team. Their ability to juggle multiple projects while staying laser-focused on the big picture made them invaluable, not just in execution but in ensuring that their work was strategically aligned with our long-term objectives.
What truly sets Kallen apart is their skill in collaborating across diverse functions. Whether working with product, design, or directly with customers, they had an exceptional ability to grasp and articulate the nuances of business needs. They consistently delivered solutions that balanced both technical depth and business acumen, creating tangible value and trust across all stakeholders.
Kallen would be a fantastic asset to any organization seeking someone who combines a strategic mindset with operational excellence and cross-functional finesse.
Anatoliy SokolenkoDirectory of Engineering @