Freelance Backend Engineers in Chicago

Freelance Backend Engineers in ChicagoFreelance Backend Engineers in Chicago

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Backend & AI Engineer | Rust, Python, Distributed Systems

New to Contra

Backend & AI Engineer | Rust, Python, Distributed Systems

Cover image for Built the real-time messaging layer

Built the real-time messaging layer for a production social platform: WebSocket chat with typing indicators, read receipts, reactions, edits, media, and live presence tracked authoritatively in Redis across a multi-worker cluster with no shared memory. Every message passes automated safety screening and encrypted storage on the hot path, with 100% delivery at p50 71ms / p99 326ms send-to-echo, and 400 concurrent sessions held with zero drops and zero errors on a single worker. Cut send latency ~3x by parallelizing ~25 serialized round-trips and moving link-preview generation off the hot path.

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Cover image for Designed, built, and shipped WeLynk

Designed, built, and shipped WeLynk solo, a production social platform live on web, iOS, and Android. Owned everything end to end: FastAPI services, PostgreSQL/Redis, React and Flutter clients, WebSocket real-time layer, deployment, and observability. The platform combines real-time chat and presence, voice and group calls, matchmaking, 10 first-party games on an in-house SDK, virtual currency, subscriptions, and internal moderation and analytics tooling. 2.1M+ lines of code across Python, TypeScript, Dart, Rust, and Luau. Zero application-caused outages since launch.

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Cover image for Built a real-time multiplayer 3D

Built a real-time multiplayer 3D engine from scratch in Rust (~294K lines): deterministic Rapier3D physics at a fixed 60Hz tick, wgpu PBR rendering to native (Metal/Vulkan/DX12) and WebGPU, and custom netcode over QUIC with delta encoding, client prediction, and rollback reconciliation for 20-player sessions. Games run in a sandboxed Luau VM, safe for untrusted code, identical logic on client and server under a strict determinism contract. One Rust core compiles to web, iOS, Android, and server. Ships with its own simulator, tick-level profiler, and telemetry analyzer.

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Cover image for Built the behavioral matchmaking engine

Built the behavioral matchmaking engine at the core of a production social platform: embedding-based profile scoring, a live match queue with presence-aware availability, and a timed decision window where both users choose to keep or release the match. Engineered for the race conditions that make live matchmaking hard: simultaneous accepts, mid-queue disconnects, and double-matching, resolved with atomic Redis operations. The engine learns from behavioral signals rather than stated preferences, with anti-bot and spam detection built into the pipeline.

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Backend Engineer(2)

Full-Stack Engineer | MVP Builds, UI/UX & Systems

New to Contra

Full-Stack Engineer | MVP Builds, UI/UX & Systems

Cover image for Reduced engineering dependency for customer

Reduced engineering dependency for customer configuration — rebuilt a deprecated portal into a flexible self-service admin system. Customers now configure real-time workflows without developer involvement. Rebuilt a legacy platform into a modular, extensible admin system with a queue builder using attribute-based routing logic, hours-of-operation management with exception handling, and a scalable architecture designed for long-term growth. MY ROLE - Led system design and frontend architecture - Implemented core admin interfaces and workflows - Collaborated on backend extensions - Drove customer adoption of new tooling DELIVERABLES - Queue builder with attribute-based routing logic - Hours-of-operation management with exceptions - Modular, extensible admin architecture RESULTS - Reduced engineering dependency for customer configuration changes - Improved scalability of onboarding and customer support workflows - Customers self-configure real-time workflows without developer involvement

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Cover image for 1–2 clicks to session start

1–2 clicks to session start — down from a multi-step fragmented flow. Zero lost inbound leads after-hours via conditional fallback UI. Used as a primary feature in revenue-adjacent sales demos. Simplified a fragmented call initiation flow into a fast, intuitive experience. Implemented progressive disclosure — clear primary CTA, minimal modal, then action. Added conditional UI based on hours of operation with an after-hours contact form fallback. Maintained across multiple customer deployments including Coloramo FCU and Chelsea Groton Bank. MY ROLE - Owned UX redesign and frontend architecture - Extended backend APIs for hours-of-operation logic - Implemented real-time UI state handling - Maintained multiple customer deployments DELIVERABLES - Progressive disclosure call initiation flow - After-hours conditional fallback UI - Live deployments at Coloramo FCU and Chelsea Groton Bank RESULTS - 1–2 clicks to session start — down from fragmented multi-step flow - Zero lost inbound leads after-hours - Adopted as a core feature in revenue-adjacent sales demos

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Cover image for 65% faster delivery — rebuilt

65% faster delivery — rebuilt a fragmented peer-to-peer video tool into a scalable conferencing system in 2 weeks instead of 6, using AI-assisted development workflows. Delivered multi-user sessions, adaptive video layouts, two-way screen sharing, and host/guest roles with waiting room and admission control. MY ROLE - Designed interaction models and system flows in Figma - Built frontend architecture and real-time state management - Implemented backend integrations — sockets, Redis, APIs DELIVERABLES - Multi-user video sessions with adaptive layouts - Two-way screen sharing - Host/guest roles + waiting room + admission control TECH STACK Vue, Vite, Pinia, Node.js, Redis, WebSockets, Figma RESULTS - 65% reduction in development timeline — 6 weeks to 2 weeks via AI-assisted workflows - 0→1 prototype transformed into a viable product system - Scalable architecture established for real-time multi-user communication

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Cover image for Cut call initiation to 1-2 clicks, zero lost leads

Cut call initiation to 1-2 clicks, zero lost leads

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Backend Engineer(3)

I design, build, and scale websites, apps, and AI products!

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I design, build, and scale websites, apps, and AI products!

Cover image for Go API Client for Bonsai.io

Go API Client for Bonsai.io

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Cover image for Terraform Provider for Bonsai.io

Terraform Provider for Bonsai.io

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Cover image for Maximizing Advertising ROI with AWS and Machine Learning: $30MM

Maximizing Advertising ROI with AWS and Machine Learning: $30MM

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Cover image for Senior Engineer training and Ruby on Rails refactoring

Senior Engineer training and Ruby on Rails refactoring

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Backend Engineer(4)

Full stack developer | DevOps | Web & Mobile App

Full stack developer | DevOps | Web & Mobile App

Cover image for Micard.io Digital Business Card Platform

Micard.io Digital Business Card Platform

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Cover image for Financial Service Platform Enhancement for HubFinance

Financial Service Platform Enhancement for HubFinance

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Cover image for CoachHub - Personal Coach Hiring Mobile App

CoachHub - Personal Coach Hiring Mobile App

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Cover image for Cash Management App

Cash Management App

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Backend Engineer(2)

Backend & DevOps Expert | Golang, Terraform, C#

Backend & DevOps Expert | Golang, Terraform, C#

Cover image for Automated Risk Assessments for Businesses

Automated Risk Assessments for Businesses

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Cover image for Created Advanced AI automations for data pipelines at Meta

Created Advanced AI automations for data pipelines at Meta

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Cover image for Building a Scalable FinTech Backend Platform

Building a Scalable FinTech Backend Platform

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Backend Engineer(3)

Sunshine Digital Solutions

Web, Apps, AI, SEO, Design, Content & Video

Web, Apps, AI, SEO, Design, Content & Video

Cover image for Trippy - AI Powered Travel Mobile Apps

Trippy - AI Powered Travel Mobile Apps

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Cover image for RevSwap Car-Swapping App Development

RevSwap Car-Swapping App Development

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Cover image for Food Delivery - Multi Restaurant - Flutter

Food Delivery - Multi Restaurant - Flutter

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Cover image for Fitness App - React Native

Fitness App - React Native

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Backend Engineer(1)

VC deal partner helping Startups build info sites and MVPs

$1k+: Earned

2x: Hired

9: Followers

Expert

Mentor

VC deal partner helping Startups build info sites and MVPs

Cover image for TokenD

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Cover image for Bolt Mentor Program

Bolt Mentor Program

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Cover image for Startup Guru

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Cover image for Cross Realty Group | Luxury Real Estate

Cross Realty Group | Luxury Real Estate

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Backend Engineer(1)

Senior software engineer

New to Contra

Senior software engineer

Cover image for SUPERHOLD Website

SUPERHOLD Website

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Cover image for Sdoge 3D Model website

Sdoge 3D Model website

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Cover image for 21TSI projects

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Cover image for igloo project

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Backend Engineer(1)