Haider Z.

Backend engineer with 3+ years shipping production systems in Go, Python, and Node.js. Top Rated on Upwork. I've built real-time bidding infrastructure processing 50K+ requests/second and backend services that handle millions of daily events across 77+ countries. What I've actually built (not hypotheticals): • A real-time bidding engine in Go that processes OpenRTB 2.x auctions under 200ms response times, running in production for a DSP serving programmatic ad campaigns. • A bot and fraud detection system that cut invalid traffic by 40%, saving ad spend by identifying non-human patterns before bids are placed. • An analytics pipeline using ClickHouse and Apache Flink that ingests millions of ad events daily and delivers real-time reporting dashboards. • AI integration layers connecting LLM APIs (OpenAI, Claude, LangChain) to existing backend services: RAG pipelines, AI agents, and tool-calling architectures. • A self-hosted Prebid Server handling header bidding auctions for multiple ad exchanges simultaneously. My stack: Go (Gin), Python (FastAPI, Celery), Node.js (NestJS), Java (Flink), Kotlin. Databases: PostgreSQL, MongoDB, ClickHouse, Redis, Aerospike. Infrastructure: Docker, AWS, Kafka, microservices. Before my current role owning the backend for an ad-tech platform, I built a real-time vehicle recovery marketplace with live GPS tracking, an NFC-based loyalty app backend (10K+ downloads), and a multi-vendor e-commerce integration platform connecting Shopify and WooCommerce stores. I work async-first, document my code, and ship working systems, not slide decks. If you need a backend engineer who's done the hard parts (real-time processing, high-throughput pipelines, AI integration), let's talk.