Available for freelance work
I Build Systems
That Scale.
Senior Backend Engineer shipping production-grade APIs, real-time data pipelines, and AI-powered SaaS platforms.
Go · NestJS · ClickHouse · Redis · LangChain · Kafka
GoNestJSTypeScriptClickHouseRedisKafkaLangChainPostgreSQL
5+Years Experience
48Repos Shipped
640+API Endpoints
8+Technologies Mastered
Technical Expertise
Built on the Right Stack
Proven in production codebase footprints across 48+ repositories. Every skill listed represents real code shipped.
⚙️
Backend & Languages
- Go (Golang)RTB engine, fraud detection, GAM harvester — 3 production services
- TypeScriptPrimary language across all NestJS & Express projects
- Node.js / NestJS311-endpoint SaaS platforms, modular architecture, DI
- Node.js / ExpressMarketplace APIs, telemetry ingestion, custom middleware
- Bun.jsUltra-low latency identity resolution & content enrichment
- PythonClickHouse data loaders, ML model training & serving
- OpenRTB 2.xBid request parsing, auction logic, SSP/DSP protocol
- REST API Design640+ endpoints designed across all projects
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Databases & Storage
- ClickHouseColumnar OLAP across 8 services — billions of events ingested
- RedisCache, Streams, Consumer Groups, Pipelining, RedisSearch, RedisJSON
- AerospikeSub-ms hot state for RTB bidder and fraud scoring
- PostgreSQLDual-DB publisher platform with 69 TypeORM migrations
- MySQLPrimary DB for Dexta SaaS, CareerPaths, evc-share
- MongoDBFraud fingerprints, session documents, variable-schema telemetry
- QdrantVector similarity search for content enrichment pipeline
- ChromaDBEmbeddings store for LangChain RAG assessment advisor
🐳
Infrastructure & DevOps
- Docker / Compose30+ service compose stacks, healthchecks, named networks
- CaddyAutomatic HTTPS reverse proxy in production stacks
- Grafana StackGrafana + Prometheus + Loki + Tempo + OnCall — full o11y
- PrometheusCustom metrics exposed on /metrics in all Go services
- Apache KafkaDurable event streaming for ML pipelines and classifier events
- BullMQFlowProducer DAG workflows, async AI jobs, email queues
- GitHub ActionsCI/CD pipelines for test + deploy automation
- MinIO (S3)Self-hosted object storage for ad creatives and log archiving
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AI & Integrations
- LangChain / LangGraphProduction RAG pipeline for recruiter AI assessment advisor
- Google Gemini AIIAB taxonomy classification + recruiter chatbot dialogue
- OpenAI APICampaign IAB taxonomy inference in advertiser classifier
- Stripe / ConnectSubscriptions, PaymentIntents, and multi-party marketplace payouts
- Google APIsGAM, GA4, Calendar, Drive, OAuth2 — all in production
- Twilio Video + SMSWebRTC video sessions + booking SMS across web & mobile
- Firebase FCMServer-side mobile push notifications for iOS & Android
- IAB TCF 2.xGDPR consent string validation in identity graph
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Frontend & Mobile
- React.jsComplex SPAs — dashboards, admin panels, assessment UIs
- Next.jsSSG/SSR for SEO-optimized portfolio and marketing sites
- React NativeCareerPaths iOS/Android app with native video + Apple Pay
- Vue.js 2 / VuetifyAdmin/professional dashboard for CareerPaths
- Redux ToolkitGlobal state for assessment session timers and question tracking
- Zustand + TanStack Query12 modular stores + API caching in publisher dashboard
- Recharts / ApexChartsTime-series, donut, bar charts across analytics dashboards
- Vanilla CSSFull design systems with CSS custom properties
98Skills Mastered
8+Database Technologies
12+Third-Party API Integrations
5+Programming Languages
Selected Work
Production Systems
I've Built
Real systems, real scale, real impact. Each project showcases a distinct area of deep technical expertise — from real-time bidding engines to AI pipelines.
⚡
Ad Tech · Real-Time Systems
2024
Real-Time Bidding Engine
Sub-200ms programmatic ad auction engine processing millions of OpenRTB 2.x bid requests daily.
<200msResponse SLA
OpenRTB 2.xProtocol
Billions of eventsData Volume
GoRedisRedisSearchClickHouseAerospike+2
View Case Study
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AI SaaS · Recruitment
2023
Dexta — AI-Powered Recruiter Assessment Platform
311-endpoint NestJS platform with LangChain RAG advisor, Puppeteer proctoring, and Stripe billing.
311API Endpoints
Gemini 2.5 FlashAI Model
3 BullMQ QueuesQueue Workers
NestJSTypeScriptLangChainLangGraphGoogle Gemini+7
View Case Study
🎯
Marketplace · FinTech
2023
CareerPaths — Mentorship Marketplace
Dual-sided marketplace with Stripe Connect payouts, Twilio WebRTC video, and Google Calendar integration.
Stripe ConnectPayment Model
Twilio WebRTCVideo Stack
Web + iOS + AndroidPlatforms
Express.jsTypeScriptStripe ConnectTwilio VideoTwilio SMS+8
View Case Study
🚙
Logistics · Real-Time Systems
2022
Winchit — Vehicle Relocation App
Real-time vehicle dispatch and relocation platform with instant and scheduled bookings.
Express + MongoTech Stack
Stripe SetupIntentsPayments
Socket.io TrackingReal-Time
Express.jsMongoDBMongooseStripeFirebase FCM+3
View Case Study
Career Journey
Professional Experience
A track record of designing, scaling, and maintaining mission-critical backend systems.
January 2026 — Present
Senior Software Engineer
Advergic•Ad Tech, SSP & DSP — Google-Certified MCM Channel Partner
- Architect and maintain a 10+ service distributed microservices platform powering a programmatic ad exchange processing hundreds of thousands of ad events daily.
- Contributed to a Go-based invalid-traffic and fraud engine performing bot detection via browser fingerprinting, IP reputation scoring, and click-timing biometric analysis.
- Built a Go-based Google Ad Manager yield harvester using OAuth2 JWT service accounts, ingesting reports into ClickHouse (ReplacingMergeTree) across multiple dimensions.
- Trained and deployed CatBoost and LightGBM models for programmatic floor-price suggestions during live bidding, served via sub-millisecond Redis cached endpoints.
- Created a Bun.js content intelligence scraper classifying page content against IAB taxonomy using Google Gemini, vector search (Qdrant), and ClickHouse caching.
- Established a self-hosted Prometheus, Grafana, Loki, Tempo, and cAdvisor monitoring stack with Slack/WhatsApp alerting.
GoNestJSClickHouseRedisKafkaMongoDBAerospikeBun.jsGrafanaPrometheusLokiTempoGoogle Gemini API
January 2022 — Present
Fullstack JavaScript Developer
Code Freaks•Digital Product Agency (UI/UX, MVPs, Tech Consulting)
- Led backend development across 10+ client project lifecycles; a source-code audit documents 640+ production REST API endpoints across these platforms (311 in a single recruitment SaaS).
- Built a production RAG pipeline for an AI assessment advisor using LangChain, LangGraph, ChromaDB, and Google Gemini for semantic conversational search.
- Engineered BullMQ job queues for proctoring analysis, AI cultural-fit scoring, report generation, and server-side Puppeteer PDF scorecard generation.
- Resolved key concurrency issues on double-submissions by engineering a Redis-based distributed lock (SET NX EX pattern).
- Integrated Stripe subscriptions, Stripe Connect multi-party payouts, Twilio WebRTC video sessions, Google Calendar API scheduling, and FCM push notifications.
- Delivered EV-charger P2P booking marketplaces, cryptocurrency community hubs, and cloud print brokers via Google Drive PDF conversion engines and the IPP printing protocol.
NestJSExpress.jsMySQLMongoDBTypeORMSequelizeBullMQChromaDBStripe ConnectTwilio VideoGoogle Calendar API
October 2021 — December 2021
Backend Intern (Node.js)
RB Sol•Technology Solutions Company
- Developed backend CRUD services for small-scale applications using Express.js, managing database interactions through Mongoose and Sequelize ORM.
- Assisted in debugging production codebases and resolving backend issues, developing foundational Node.js skills in a professional environment.
Node.jsExpress.jsMongoDBMongooseSequelize
Get In Touch
Let's Build Together
Have a system that needs scaling, an API integration that needs building, or a ClickHouse analytics cluster that needs tuning? Get in touch.
✉️
Direct Emailfarzankhan009@gmail.com
📞
Phone / WhatsApp+92 316 148 0849