John Costa

ExecOnline · Remote

Hands-on leadership role focused on technical architecture and team mentorship, similar in scope to a Staff or Lead Engineer at most product companies.

• Led a cross-functional team of 8 engineers (iOS, React/TypeScript, Rails) to deliver key initiatives including an AI chat builder, full platform reskin with Storybook, a learning insights dashboard, and iOS enhancements.
• Rebuilt the Learning Collection Builder into a real-time, AI-powered single-page app, replacing a slow multi-step wizard. Used client-side in-memory dictionaries to eliminate round trips and reduced publish time from several minutes to under 3 seconds.
• Led integration of TanStack Query to implement client-side caching with background revalidation, reducing perceived load times on key pages by up to 90% (8s to under 1s) and cutting redundant server requests by approximately 40%.
• Took initiative to evaluate emerging AI development tools, leading the collaborative adoption of Cline, which significantly boosted developer productivity and sparked a broader shift toward writing AI-friendly, well-structured code.

ExecOnline · Remote

• Led approximately 95% of code reviews during a 3x team expansion (9 to 25 developers) and mentored 16+ engineers in functional programming via code examples, internal videos, and architecture talks.
• Advanced engineering standards by introducing type-safe patterns, mentoring new hires, and leading internal talks, strengthening design fluency and code clarity across the organization.
• Architected the end-to-end Stripe payment flow for a new B2C offering, enabling instant user access post-purchase with multi-step reconciliation using real-time Pusher WebSockets.
• Improved code quality through extensive refactors, internal tooling, and advocating strong typing as a foundation for correctness, complemented by targeted Jasmine and RSpec unit tests.
• Enhanced security and modernized the application stack by upgrading dependencies, automating workflows via GitHub Actions, and consolidating common logic into reusable shared libraries.

ExecOnline · Remote

• Built a scalable video authoring pipeline using AWS Step Functions, Lambda, and Bitmovin API. Introduced a reusable video library model, reducing redundant uploads by 80% and saving teams dozens of hours monthly.
• Architected a robust video delivery system with adaptive playback via JW Player, multi-tiered fallbacks, and configurable provider overrides, reducing playback failures by over 90% and improving average video start time by 30%.
• Enabled ExecOnline's transition to a scalable SaaS platform by leading the shift from scheduled to on-demand programs, boosting client program utilization by over 50%.

ExecOnline · San Francisco, CA

• Built and maintained core features of the ExecOnline platform during a high-growth phase, contributing to both backend systems in Ruby on Rails and frontend functionality using JavaScript, jQuery, and early React.
• Co-led development of the Enterprise Portal, a new internal-facing platform to manage participant enrollment, content authoring, and course operations.
• Championed incremental modernization of the codebase, advocating for stronger separation of concerns and gradually introducing React-based interfaces for better UX and maintainability.
• Maintained high code quality through robust automated testing with RSpec and Jasmine, consistently achieving over 85% test coverage for critical systems.