Павел Голдин
Backend Engineer · Fintech / Crypto / Logistics
New to Contra
Павел is building their profile!
Ad Tech Platform
Setting up one ad campaign took 4 hours of manual work. Traffic data arrived with a 24-hour delay.
Built FastAPI backend for config orchestration. Redis cache for heavy aggregations. Real-time dashboard via async event processor.
Setup time: 240 min → 15 min. 100% uptime throughout the engagement.
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Digital Design Studio
Legacy CMS couldn't handle high-resolution media assets, pages took over 6 seconds to load.
Built Django REST API + FastAPI media pipeline. Async processing of uploaded files. React SPA with CDN delivery and client-side caching.
Page load: 6s → 1.2s. Lighthouse 97/100 in production. 4K media assets with no delays.
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Logistics company.
Shipment statuses updated manually, clients called to ask where their cargo was.
Built FastAPI tracking service with WebSocket for real-time updates. Celery workers with retry mechanisms for polling external APIs. Idempotent keys on every event. Redis Pub/Sub for broadcasting statuses to clients.
Zero data loss on external API failures. Manager workload reduced by 70%. Uptime 99.9%.
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Crypto Payment Backend
Cryptocurrency platform with unreliable transaction processing — duplicate credits appearing under high load.
Built event-driven backend: idempotent keys on every credit operation, async verification via Celery with exponential retries, SELECT FOR UPDATE NOWAIT on balance operations. Webhook queue with guaranteed delivery.
Zero duplicate credits over 8 months in production. Throughput x4. Webhook delivery 100%.
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