Robert Lehmann
Verified Expert in Engineering
Full-stack and Unity3D Game Developer
Berlin, Germany
Toptal member since September 13, 2022
Robert is a passionate gamer, experienced director of engineering, and blockchain enthusiast with 10+ years of professional experience and a bachelor's degree in game design. He has developed two multimillion-dollar-grossing games in Unity3D, published on Google Play and the App Store: Solitaire Showtime and Mahjong City Tours, which has over 25 million downloads. Robert has also developed unique smart contracts and dApps across different blockchains.
Portfolio
Experience
- Programming - 12 years
- C# - 10 years
- Unity - 10 years
- Computer Science - 10 years
- JavaScript - 7 years
- Amazon Web Services (AWS) - 6 years
- CI/CD Pipelines - 6 years
- Serverless Architecture - 6 years
Preferred Environment
Unity, React, Amazon Web Services (AWS), Gaming, Unity3D, Virtual Reality (VR), Unity SDK, Technical Design, Technical Architecture, Payment APIs, CTO, Full-stack, Firebase, Mobile Development, Analytics, Google Analytics, Python, C#, .NET, Bots, Discord Bots, Telegram Bots, AWS Lambda, WebGL, MMORPGs, Serverless, Back-end, Source Code Review, Code Review, AWS Cloud Architecture, 3D Games, C++, Games, Amazon DynamoDB, Amazon S3 (AWS S3), Web Security, Web Scraping, Unity2D, Mobile Games, Unity3D Native Plugin Interface, JSON, DevOps, Mobile Apps, 2D, WebView, User Authentication, Cryptocurrency Wallets, MetaMask, Blockchain, API Integration, Integration, C#.NET, Lambda Functions, Game Development, Gameplay Development, Mobile App Development, Google Play Store, Non-fungible Tokens (NFT), Smart Contracts, RPG, Gamification, Mathematics, Cross-platform App Development, Vercel, Rust, Crypto, Apache Kafka, OpenAI GPT-3 API, OpenAI GPT-4 API, OpenAI, ChatGPT, Character Rigging, Google Bard, Blockchain & Cryptocurrency, ERC-1155, Mobile Applications, Lua, Large Language Models (LLMs), WhatsApp API, Web Forms, Forms, MacOS, ActionScript 3, Flash ActionScript, Visual Studio, OpenAI API, AI Integration, React-JSS, AI Agents, PyTorch, Finance, Server-side PDF Generation, AI Tools, Booking.com API, Booking, Microsoft Teams, Claude, Cursor AI, Claude API, AI-generated Code, Claude Code, Stripe Connect, ComfyUI, Astro, Agentic AI Systems, Prompt Engineering, Containers, Amazon Bedrock AgentCore, AI-assisted Development, HIPAA, Playwright
The most amazing...
...thing I've developed is Mahjong City Tours, a mobile game with over 25 million downloads on Google Play and the App Store.
Work Experience
Full-stack Engineer (API Integrations)
Fifty 410, LLC
- Architected a serverless pharmacy management platform on Cloudflare Workers, D1, KV, R2, Queues, and Durable Objects, serving staff, provider, and patient portals.
- Integrated five pharmacy networks (LifeFile, PerfectRx, HealthWarehouse, PharmacyHub, and EpiqScripts) into a unified order-routing layer with webhook-driven status tracking.
- Built a HIPAA-compliant TypeScript monorepo with PBKDF2 hashing (100,000 iterations), rate-limited auth (5-attempt lockout), session concurrency limits, and full audit logging.
- Optimized payment dashboard load times around 50x by caching data in D1 and replaced an O(n²) duplicate-detection algorithm with SQL-optimized queries supporting bulk merge.
- Delivered real-time support inbox and patient chat using Durable Objects WebSockets with auto-reconnect, read receipts, and R2-backed file attachments.
- Engineered an automated prescription refill system tracking end dates and grouping multiple expiring medications into a single reminder email sent seven days before expiration.
- Authored 20+ Playwright end-to-end test suites covering auth, payments, multi-pharmacy workflows, and provider portals to safeguard critical clinical paths.
- Managed 60+ versioned D1 database migrations across payments, chat, intake forms, health tracking, and pharmacy integrations with zero-downtime schema evolution.
CTO
Calumma Games
- Architected a modular Unity game client from a large suite of custom C# assembly modules, powering multiple 2D and 3D puzzle titles from one shared codebase by decoupling core systems from per-game logic.
- Designed and deployed a serverless, real-time multiplayer back end on AWS using WebSocket APIs, DynamoDB, managed Redis-compatible caching, and Lambda, delivering live leaderboards, clubs, and tournaments at low latency across multiple environments.
- Built a high-volume analytics pipeline streaming gameplay events through managed ingestion into a serverless data warehouse, modeling a broad set of event schemas to enable cost-efficient, auto-scaling storage and granular player-behavior analysis.
- Developed a config-driven machine learning framework for churn, lifetime-value, and economy-health prediction using gradient-boosted models with explainability tooling and automated, human-readable LLM result summaries.
- Engineered a live-ops control plane in React with a modular state architecture and server-state caching, giving the team a schema-driven editor to tune game economy, levels, and themes in real time without app-store releases.
- Implemented a "configuration-as-code" data pipeline that transforms spreadsheet-based source data into validated configuration and generates strongly typed client code, guaranteeing end-to-end type safety between live-ops tooling and game clients.
- Integrated a cross-platform monetization and anti-fraud stack, combining client-side ad mediation, in-app purchasing, and commerce SDKs with server-side store-receipt and platform-integrity verification.
- Adopted a modern, leading-edge web stack across public-facing and internal tooling, and stood up a managed build-distribution platform with browser-side mobile-package parsing for automated release ingestion.
- Hands-on experience with Temporal workflow orchestration in production environments, including long-running workflows, failure recovery, retry policies, worker autoscaling, and distributed system reliability.
- Optimized Temporal-backed PostgreSQL systems by improving workflow throughput, reducing database contention, tuning indexes and queries, implementing PgBouncer, and scaling high-volume async workloads.
Associate Director, Engineering
Jam City
- Built client applications for Mahjong City Tours and Solitaire Showtime in Unity3D, including native-level requirements, such as ads and mobile notifications.
- Developed the back end for Mahjong City Tours and Solitaire Showtime as a serverless application within AWS (Lambdas, DynamoDB, etc.) combined with other services like Firebase.
- Set up the overall pipeline for the Berlin Studio, including automated client builds per merged Git patch sets with distributions to test users and a simple interface for engineers to deploy personal back ends using AWS CloudFormation.
- Identified and fixed memory leaks across the front end and back end (Node.js) to decrease user-facing issues and reduce the overall costs of services.
- Developed an in-house solution for LiveOps, including an easy-to-use interface for the PM and handy ways for artists to deploy on-demand assets into the LiveOps pipeline for later use, such as offers.
- Built analytical tracking mechanisms and dashboards to analyze the overall performance of any product using Databricks and SQL.
- Implemented 3D Secure 2.0 authentication for MasterCard to increase the security of online transactions and comply with industry standards.
- Oversaw a split system where the client (mobile app) was doing transactions. Fetched the challenge data per HTTPS request and sent it to our back end for further validation, where we checked it with the 3D secure vendor data.
- Implemented various Visa APIs like Visa Payments Processing APIs to enable direct credit card payments for both mobile and web applications.
- Ensured seamless transitions as an adept at the Maya-to-Unity animation pipeline. My profound expertise in Unity's animation systems centers on character animation, enhancing gameplay realism.
Experience
Mahjong City Tours
https://www.jamcity.com/game/mahjong-city-tours/Solitaire Showtime
https://www.jamcity.com/game/solitaire-showtime/Equity Token
The Equity dashboard provides easy, user-friendly options to review or change contract-related data based on the connected wallet.
Vault
https://www.vault.technology/Education
Bachelor's Degree in Game Design
Mediadesign Hochschule - Berlin, Germany
Certifications
AWS Certified Developer Associate
AWS
Skills
Libraries/APIs
React, Node.js, WebGL, REST APIs, Google Calendar API, AWS Amplify, OpenAPI, Vue, D3.js, Social APIs, Exchange API, Stripe, OpenGL, Google Maps, Google Maps API, Facebook API, API Development, Web API, Google Sheets API, OpenAI API, React-JSS, Google Maps SDK, Claude API, Stripe Connect, Vue 3, CocoaPods, jQuery, Twilio API, WebRTC, Web3.js, Binance API, Chart.js, Plaid API, X (formerly Twitter) API, Shopify API, PostgREST, Stripe API, Instagram API, Java Servlets, WhatsApp API, PyTorch, Booking.com API, Gmail API, Playwright, Liquid, vLLM, Three.js, Matter.js, XGBoost, Scikit-learn, Pandas, MRAID, Zod, Google Play API
Tools
Unity SDK, Figma, Google Analytics, WebView, Amazon CloudFront CDN, MetaMask, Cron, Amazon Cognito, Microsoft Excel, Spreadsheets, Microsoft Visual Studio, Gradle, GitHub, Amazon CloudWatch, Git, AWS IAM, Amazon Simple Queue Service (SQS), Jira, Confluence, Amazon ElastiCache, Amazon Simple Notification Service (SNS), AWS Fargate, AWS CloudFormation, Google Sheets, Prisma, Autotask, Character User Interface (CUI), Amazon CloudFront, Webpack, AWS Cloud Development Kit (CDK), Firebase Authentication, Amazon Elastic Container Service (ECS), AWS Step Functions, Auth0, Visual Studio, TestFlight, Microsoft Teams, Expo, Claude, Amazon Virtual Private Cloud (VPC), n8n, Microsoft Web Services, Microsoft Graph, GitLab CI/CD, Claude Code, Qualtrics, Firebase Cloud Messaging (FCM), Codex, Xcode, Remix IDE, Google Assistant, Unreal Development Kit (UDK), DataRobot, BigQuery, Postman, Dialogflow, Amazon SageMaker, Plaid, AWS AppSync, Puppet, ChatGPT, Terraform, Redux Toolkit, Shadcn, Android Profiler, Grafana, Nx, SendGrid, Apache, ComfyUI, Astro, Zapier, Autodesk FBX SDK, Maya, Google Bard, Shadcn UI, Cocos Creator, Spine, JSON Schema, Vitest
Languages
C#, JavaScript, SQL, HTML, CSS, TypeScript, Swift, Python, PHP, C++, C#.NET, Kotlin, HTML5, Java, Groovy, RPG, XML, ECMAScript (ES6), Lua, Objective-C, Sass, GraphQL, Snowflake, Dart, Visual Basic, C++/CX, Rust, Solidity, Go, CSS3, ActionScript 3, Flash ActionScript, Erlang, GLSL
Frameworks
Unity, Unity3D, .NET Core, Swagger, .NET, Next.js, OAuth 2, ASP.NET MVC, Unity2D, React Native, Express.js, Material UI, Unreal Engine, Flutter, NestJS, Angular, Ruby on Rails (RoR), Android SDK, ASP.NET, ASP.NET Core, PixiJS, .NET MAUI, iOS SDK, Laravel, Tailwind CSS, Photon Unity Networking (PUN), Unity 3, SwiftUI, Nuxt.js, Spring Boot, Photon, ARKit, Unreal Engine 4, Django, Grails, Blueprint, Redux, Jest, gRPC, Electron, Flask, Truffle, Hardhat, Payload CMS, CodeIgniter, AngularJS, Blazor, Cypress, Bootstrap, Svelte, Parity Polkadot, MUI CSS, Box2D, LightGBM, Jinja
Paradigms
Serverless Architecture, Mobile Development, Database Design, Back-end Architecture, DevOps, Scrum, REST, Cross-platform, Model View ViewModel (MVVM), Responsive Layout, Object-relational Mapping (ORM), Mobile App Design, Gamification, Microservices, Mobile Game Design, Agile, Agile Software Development, Unit Testing, Test-driven Development (TDD), Asynchronous Programming, Requirements Analysis, Agile Project Management, Event-driven Architecture, Lambda Architecture, Microservices Architecture, UX Design, API Architecture, Microinteractions, Web Architecture, Automation, UI Design, Model Context Protocol (MCP), Role-based Access Control (RBAC), Continuous Delivery (CD), Continuous Integration (CI), Web Performance Optimization (WPO), Desktop App Development, Responsive Web Design (RWD), MEAN Stack, Testing, HIPAA Compliance, Web UI Design, Web UX Design, ETL, Real-time Systems
Platforms
Amazon Web Services (AWS), Azure, iOS, Android, Firebase, AWS Lambda, Mobile, Blockchain, Ethereum, Amazon EC2, Windows, Google Cloud Platform (GCP), Azure Functions, Azure PlayFab, Microsoft, Google AppSheet, Xamarin, Visual Studio Code (VS Code), MacOS, Cloud Run, AWS Elastic Beanstalk, Amazon Alexa, AWS IoT, Xbox, PlayStation, Bluetooth Low Energy (LE), Joomla, Vercel, Docker, Oculus, WordPress, Kubernetes, Databricks, FlutterFlow, Linux, Shopify, Typesafe, PostHog, Mapbox, WooCommerce, Apache Kafka, Twilio
Storage
MongoDB, NoSQL, Databases, MySQL, Amazon DynamoDB, Amazon S3 (AWS S3), JSON, PostgreSQL, Cloud Firestore, Redis Cache, Azure SQL Databases, Graph Databases, Database Architecture, Azure SQL, Azure Queue Storage, Redis, Azure Cloud Services, Unity Cloud Build, Database Management, Redshift, Web Forms, Cloud Deployment, Firebase Realtime Database, Company Databases, Google Cloud, IIS SQL Server, Data Integration, Elasticsearch, Data Pipelines, SQL Anywhere, SQLite, Database Migration
Industry Expertise
Project Management, Binance Cryptocurrency Exchange, Web Design, Healthcare
Other
Programming, Game Design, Computer Science, CI/CD Pipelines, Architecture, Gaming, APIs, User Interface (UI), Technical Design, Technical Architecture, Payment APIs, CTO, Full-stack, Analytics, Front-end, Memory Leaks, Proof of Concept (POC), Serverless, Back-end, Security, Source Code Review, Code Review, Project Consultancy, AWS Cloud Architecture, AWS Certified Developer, 3D Games, Games, Web Security, Mobile Games, Unity3D Native Plugin Interface, Data Visualization, Interactive UI, Mobile Apps, 2D, User Authentication, Amazon RDS, Headless Software, Virtual DOM, Cryptocurrency Wallets, API Integration, Integration, Leadership, Team Leadership, Lambda Functions, Exports, MERN Stack, Technical Leadership, Mobile Game Development, Software Architecture, CSV, Calendars, Smart Homes, Smart Devices, Unreal Engine 5, Game Development, Gameplay Development, Artificial Intelligence (AI), Adaptive Design, Mobile App Development, Apple Numbers, Multiplayer, Web Development, Design, Discord, Google Play Store, Smart Contracts, Ethereum Smart Contracts, Firebase Cloud Functions, Front-end Development, Reverse Engineering, Software Design, Scalable Architecture, Back-end Development, 3D Rendering, 3D, WebSockets, Mobile UX, User Experience (UX), SDKs, Application Engineering, Authentication, Cryptography, Decentralized Applications, Mathematics, Casino Games, Cross-platform App Development, UI Components, Single Sign-on (SSO), Amazon Neptune, Web UI, Chatbots, Mobile Architecture, Data Architecture, Cloud Architecture, Amazon API Gateway, Android Game Development, Crypto, Algorithms, Data Structures, Trading, Azure Data Lake, Data Engineering, Unity Game Assets, In-app Purchases, Cloud, Minimum Viable Product (MVP), Early-stage Startups, Game AI, Slack App, Slackbot, Amazon Cognito User Pools, Full-stack Development, State Machines, Character Animation, Video Gaming, Distributed Systems, Blockchain & Cryptocurrency, ERC-1155, Abstract Syntax Trees (AST), Plugins, Extensions, 2D Games, Video Games, Game Programming, Memory Profiling, Optimization, Performance Optimization, Decentralized Finance (DeFi), Web3, ECS, Social Security, API Design, AI Chatbots, Mobile Applications, Large-scale Projects, FastAPI, Reporting, Decentralized Systems, Engineering, Amazon EventBridge, Supabase, Responsive UI, Scaling, Web Applications, Microsoft Azure, Startups, Cloud Infrastructure, Data Modeling, GitHub Actions, Infrastructure, Forms, API Gateways, Ethers.js, Virtual Private Servers, Solution Architecture, AI Integration, RESTFul APIs, Identity & Access Management (IAM), iGaming, Customer Relationship Management (CRM), React Unity WebGL, AI Agents, Google Maps Styling, Server-side PDF Generation, AI Tools, Figma to React, Styled-components, Amazon Redshift, Mobile First, App Store, MVP Design, Blockchain Security, ÐApp, Scripting, Web Servers, System Design, Apple Pay, AWS Secrets Manager, AWS Database Management System, Architectural Design, Fractional CTO, Scalable Platforms, AI-enabled Applications, Advisory, Communication, Orchestration, PayPal, Command-line Interface (CLI), Microsoft Graph API, Mobile GPS, Push Notifications, Activity Feeds, Stripe Payments, Stripe Subscriptions, Application State Management, Observability, AI-generated Code, Third-party APIs, Third-party Integration, Troubleshooting, Workflow, Workflows, Gemini, Prompt Engineering, Generative Artificial Intelligence (GenAI), Website Performance, AI-assisted Development, Containerization, Multitenancy, SMS, Database Optimization, Anthropic, Universal Render Pipeline (URP), Authorization, Database Schema Design, Vibe Coding, Code Auditing, Scalability, IT Infrastructure, SaaS, Virtual Reality (VR), Heatmaps, Bots, Discord Bots, Telegram Bots, Webhooks, MMORPGs, Networking, OAuth, Augmented Reality (AR), LiDAR, Web Scraping, Charts, Interactive Maps, Payment Gateways, Live Chat, Progressive Web Applications (PWAs), Decision Trees, Lottie, Machine Learning, Internet of Things (IoT), Responsive Web Apps, SSL Certificates, Windows Desktop Software, Non-fungible Tokens (NFT), Data Analysis, Web 3.0, Tokenomics, Cryptocurrency, Axios, Card Payments, 3D Secure, 3D Secure 2.0, Near-field Communication (NFC), Secure Storage, Chrome Extensions, Natural Language Processing (NLP), Natural Language Understanding (NLU), Generative Pre-trained Transformers (GPT), Accessibility, Location Services, Audio, Online Payments, Web Platforms, SVG, OpenAI GPT-3 API, OpenAI GPT-4 API, Server Security, WebAuth, Secure Multi-party Computation, Data Analytics, 360° Video, Photogrammetry, VR Interfaces, QA Testing, OpenAI, Visual Effects (VFX), Character Rigging, Web UX, Workflow Automation & System Integration, WebAssembly (Wasm), UDP, TCP/IP, Blueprints Visual Scripting, UI Blueprints, Solana, Text-to-Speech (TTS), ChatGPT API, Dashboards, Cryptocurrency Trading, Large Language Models (LLMs), Payment Processing, DApps, Game Engine Programming, Queue Management, Application Performance Monitoring, Real-time Data, Speech-to-Text (STT), Document Parsing, Finance, Booking, eCommerce, Location Tracking, GPS, Site Speed Optimization, Cursor AI, Online Banking, SMTP, Airtable, Agentic AI, Retrieval-augmented Generation (RAG), Optical Character Recognition (OCR), ReAct Agents, Cordova, Agentic AI Systems, Cloud Computing, Agentic Workflow Design, Temporal, Containers, Amazon Bedrock AgentCore, .NET 10, HIPAA, RAG Systems, Healthtech, Vector Databases, Terraform Cloud, SAP, Video Streaming, Apollo, LangChain, 3D Animation, LiveOps, React 19, Zustand, TanStack Query, Vite, Rapier3d, Amazon Kinesis, Data Warehousing, Infrastructure as Code (IaC), Caching, Playables, Shaders, Physics, MSW, Biome, App Store Connect, Xsolla, Cloudflare, Cloudflare D1, Cloudflare R2, Cloudflare KV, Cloudflare Durable Objects, Cloudflare Queues, Monorepos
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