Senior software engineerbuilding systemsthat scale.

I'm Borislav Koprinski, a senior software engineer who has been shipping software since 2014. As CTO at 1ForFit, I led the team in scalability and process, keeping our technology ahead of a fast-moving industry.

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System DesignScalabilityArchitectureTeam LeadershipProcess & DeliveryReliability

Projects

Jan 2026 - present·6 min read

Multi-tenant SaaSPHP / LaravelVue / Inertia

Built a QR-to-reward loyalty platform with a habit loop that brings back 69% of the customers

69%

of registered customers came back more than once

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Jan 2020 - present·6 min read

Multi-brand platformPHP / LaravelConversion funnel

Built the quiz-to-checkout engine behind 10 personalized-diet brands selling in 180 countries

180

countries reached, across ~10 diet brands

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Aug-Nov 2023·4 min read

Distributed SystemsMongoDBReal-time

Cut cross-region read latency from ~280 ms to under 10 ms with geo-sharded MongoDB

28×

faster reads for transcontinental users

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Nov-Dec 2020·4 min read

Event PipelineServer-Side TrackingNode.js

Built a server-side tracking pipeline delivering up to ~1M events/day to 5 ad and analytics platforms

~1M

events/day at peak

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Experience

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1ForFit

Owned technology as CTO of a global health and wellness product (diet, training, online coaching, longevity) with 300,000+ subscriptions and 1M+ visits. I grew the engineering team to 25 people across several countries and set the direction on architecture, code review, and mentoring, while staying hands-on with the hardest problems. When Stripe abruptly closed our account, I migrated 100,000+ live subscriptions and all payment tokens to Braintree within days, with zero customer disruption. I also led the re-architecture of the legacy payment and profile systems into a clean Laravel application (OOP, SOLID, DDD) and scaled the platform worldwide with per-locale MongoDB sharding and regional Google Cloud servers.

Team of 25ArchitecturePaymentsMongoDBGoogle CloudScale

Grew into a leadership role: led a small engineering team, set code-review and engineering standards, and mentored while staying deep in the code. Drove the payment platform forward, integrating 8+ providers (Stripe, Braintree 3DS, PayPal, Adyen, DLocal, ChargeBee, Apple Pay, Google Pay) behind the Primer orchestrator, with a subscription billing engine that charged hundreds of thousands of subscriptions reliably.

Team leadershipPHP / LaravelPayments (8+ providers)PrimerMentoring

Built core backend systems from the ground up: payment integrations, subscription flows, and a server-side event-tracking pipeline that delivered up to ~1M events/day to multiple ad and analytics platforms. Clean Laravel and Node.js, applying OOP, SOLID, and DDD for long-term maintainability.

PHP / LaravelNode.jsMongoDBEvent pipelinesDDD

Proxima-3

A casino and gaming software house building commercial desktop, embedded, and systems software sold across Europe and Latin America. I designed and owned the architecture of a casino accounting and authorization system (C++, Qt, SQLite3) sold commercially in Bulgaria, Romania, Hungary, and Mexico, and delivered 20+ slot games and an embedded reel-game system (C, OpenGL/3D, Linux, Raspberry Pi), working from low-level embedded code up to full application architecture.

C++ / QtC / OpenGLEmbedded / LinuxSQLite3

UMBAL Kanev Hospital

Administered the hospital's systems. On my own initiative, I spotted a weakness in the fingerprint-based hospitalization process and built a PHP and MySQL web app to fix it.

System administrationPHP / MySQL

Omisoft Ltd.

Built VitaBox, a full-stack set-top-box platform for TV and entertainment (Java/Play, PostgreSQL, AngularJS, WebRTC live chat), using MVC and core design patterns with clean, well-tested code.

Java / PlayAngularJSPostgreSQLWebRTC