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David Kiss
Verified Expert in Engineering
Software Engineer and Developer
Toronto, ON, Canada
Toptal member since June 9, 2014
Bio
David is a result-oriented, pragmatic, senior software engineer specializing in Python, FastAPI, and AI engineering, with 18+ years of back-end experience in multiple stacks. He's recently designed and built production-grade Python back ends and AI-powered apps. A former Java/Spring Boot lead, now focused on Python ecosystems, React/Next.js front end, and AI-driven innovation, he has proven ability to ship robust systems quickly, mentor teams, and architect scalable cloud-native solutions.
Portfolio
Roger Healthcare
Python 3, TypeScript, MongoDB, React, React Native, Expo, Cursor AI
SportEdge
Python, AWS Lambda, PostgreSQL, GitHub Actions, AWS Step Functions...
WrkSense
TypeScript, LangChain, Azure Cosmos DB, Vector Search, ChatGPT, Llama 3, Groq...
Experience
- JavaScript - 8 years
- SQL - 7 years
- Architecture - 5 years
- React - 2 years
- Node.js - 2 years
- Python 3 - 2 years
- FastAPI - 1 year
- LangChain - 1 year
Preferred Environment
Amazon Web Services (AWS), Python, AWS Lambda, React, Artificial Intelligence (AI), LangChain, Generative Artificial Intelligence (GenAI), FastAPI, LangGraph, Next.js
The most amazing...
...decision for my career has been to continuously learn and grow so that I get to work on more challenging and complex tasks and provide more value to my clients.
Work Experience
Full-stack Engineer
2025 - 2025
Roger Healthcare
- Built logic to persist transcribed patient details (allergies, wounds, patient goals, etc.) to SQLite on Android and implemented logic to verify business logic using Appium Inspector.
- Refactored the React Native front-end code to be more robust, performant, and maintainable, and migrated code from JavaScript to TypeScript.
- Got the team to migrate the FastAPI back end from running in Docker containers on EC2 instances to running on AWS ECS containers to save on maintenance efforts and operational costs.
Technologies: Python 3, TypeScript, MongoDB, React, React Native, Expo, Cursor AI
CTO
2024 - 2024
SportEdge
- Designed and led the building of the company's data pipeline to automatically ingest data for golf analytics.
- Set up infrastructure in AWS using infrastructure as code (IaC).
- Migrated existing data to a new PostgreSQL DDL structure.
Technologies: Python, AWS Lambda, PostgreSQL, GitHub Actions, AWS Step Functions, Data Pipelines, Pandas, AWS Cloud Development Kit (CDK), Serverless, Startups, DevOps, REST APIs, Docker, CI/CD Pipelines
AI Engineer
2024 - 2024
WrkSense
- Built a feature using AI to quickly parse resumes by extracting names, emails, phone numbers, locations, and time zones from .pdf, .doc, and .docx resume files.
- Built a feature using AI to parse .pdf, .doc, and .docx resumes, including name, email, URLs, summary, skills, languages, work experiences, education, training, certifications, references, and awards.
- Generated standardized .pdf resume files using parsed resume details as a feature using AI.
- Matched resumes with jobs using vector search as a feature using AI.
- Scored resumes based on recruiters' custom list of criteria (years of experience, skills, location, certifications, etc.) for a specific job as a feature using AI.
Technologies: TypeScript, LangChain, Azure Cosmos DB, Vector Search, ChatGPT, Llama 3, Groq, Gemini, Claude, Node.js, Express.js, Gemini API, Startups, Full-stack, NoSQL, REST APIs, API Integration, OpenAI
AI Engineer
2024 - 2024
ArrowHQ
- Reduced latency to enable real-time conversation between bot and IVR menu and customer service rep.
- Resolved the issue of the IVR bot not "understanding" digits spelled by our bot.
- Introduced Groq and Llama for faster intent recognition in messages from customer support reps.
- Added regression tests to help iterate faster on prompt engineering.
Technologies: Python, FastAPI, ChatGPT API, ChatGPT, ChatGPT Prompts, Groq, Meta Llama, Deepgram, TypeScript, Node.js, PostgreSQL, GitHub Actions, Amazon Web Services (AWS), Amazon Aurora, Startups, REST APIs, Docker, OpenAI
Lead Software Engineer
2023 - 2024
Condor Software
- Developed the full stack of a complex feature for a SOX-compliant accounting application, including a React front end, back-end Python REST API endpoints, Django SQL queries, and a test suite.
- Optimized infrastructure, including a GitHub Actions CI/CD pipeline and AWS CloudFormation IaC.
- Mentored other engineers and introduced the DangerJS tool to help automate manual PR review tasks.
Technologies: Python, Django, TypeScript, React, Amazon Web Services (AWS), AWS CloudFormation, PostgreSQL, GitHub, MUI CSS, CSS, HTML, SQL, Agile Software Development, Unit Testing, Continuous Integration (CI), REST, Amazon S3 (AWS S3), Visual Studio Code (VS Code), Architecture, Scrum, Startups, Full-stack, DevOps, REST APIs, Docker, Material UI, CI/CD Pipelines
Director of Engineering
2022 - 2022
RBC
- Coordinated deliverables with the product team, 3rd-party software vendor, solution architect, and tech team.
- Pushed the delivery team to build a project plan fast and collaborated with the delivery and product teams, solution architects, a 3rd-party vendor (LivePerson), and other dev teams to project plans for conversational flows and back-end integrations.
- Assisted the solution architecture team in exploring an existing solution that could be reused for our project when they faced resource constraints.
- Aided the back-end team in delivering the back-end integrations a week before a scheduled release date after the team lost one of the two back-end developers.
Technologies: JavaScript, Node.js, IT Strategy, Leadership, Strategic Planning, APIs, SQL, Agile Software Development, Continuous Integration (CI), REST, OpenShift, Scrum, LivePerson, Full-stack, REST APIs, API Integration
Senior Software Engineer
2021 - 2022
Nuvalence
- Headed load-testing efforts to sync 5,000 messages per second from Google Cloud to Azure.
- Built a POC to identify personally identifiable information (PII) in images and PDF files using the Cloud Data Loss Prevention (DLP) service.
- Created a Docker container to migrate data from Azure SQL to Google Cloud SQL automatically.
Technologies: Java, Spring Boot, Node.js, Google Cloud, Azure, JavaScript, TypeScript, Amazon Web Services (AWS), AWS Lambda, Serverless Framework, Spring MVC, APIs, Spring, Microservices, SQL, Agile Software Development, Unit Testing, Continuous Integration (CI), REST, Java 8, Amazon S3 (AWS S3), Architecture, Scrum, Serverless, Google Cloud Platform (GCP), DevOps, NoSQL, REST APIs
Lead Java Developer
2021 - 2021
P C Financial
- Headed a pod of two Java developers on the back-end team.
- Proposed several solutions to improve the back-end team's velocity and reduce operational costs.
- Built a prototype for a web application to help the bank's customers earn more loyalty points as part of the bank's hackathon.
Technologies: Spring, Microservices, Java 9, Groovy, Oracle, OpenShift, Jenkins, Gradle, Kubernetes, Helm, Spring MVC, Spring Boot, Architecture, APIs, SQL, Agile Software Development, Unit Testing, Continuous Integration (CI), REST, Java 8, Leadership, Scrum, REST APIs
Principal Engineer
2019 - 2020
DrFirst
- Designed and built a full-stack application that allows customers to retrieve audit records.
- Integrated the company's mobile app with major electronic medical records (EMR) vendors to help patients import their health records into a single central place.
- Conducted interviews at the request of other teams to help them hire qualified candidates.
Technologies: Java 8, Spring, PostgreSQL, HL7, Amazon Web Services (AWS), Amazon S3 (AWS S3), Angular, MongoDB, TypeScript, Spring Boot, Spring MVC, Architecture, APIs, Microservices, CSS, HTML, SQL, Agile Software Development, Unit Testing, Continuous Integration (CI), REST, HL7 FHIR Standard, Scrum, Full-stack, REST APIs
Software Developer and Architect
2018 - 2019
Deloitte Canada
- Worked on several middle-tier projects with both software developer and architect capabilities.
- Proposed a design for an API gateway for seamless OAuth token exchange between Okta and other identity providers.
- Suggested reliable communication between the mobile app and the back end for users to enter video conference calls with doctors.
Technologies: Node.js, Firebase, Google Cloud, OAuth, SQL, Spring Boot, Java, Spring MVC, Architecture, APIs, Spring, Microservices, Hibernate, Agile Software Development, Unit Testing, Continuous Integration (CI), REST, Apache Maven, Java 8, Kubernetes, Helm, Spring Security, Scrum, GraphQL, Google Cloud Platform (GCP), REST APIs
Lead Back-end Developer
2015 - 2018
RBC
- Led the design and development of several middle-tier applications under the RBC reward and loyalty organization.
- Managed a team of nine Java back-end developers working on 2-3 different middle-tier projects simultaneously.
- Oversaw the overall application architecture, code quality, and optimal productivity of the back-end team.
Technologies: Cloud, Apache Camel, SQL, Microservices, Spring Boot, Java, Spring MVC, Architecture, APIs, Spring, Hibernate, Agile Software Development, Unit Testing, Continuous Integration (CI), REST, Apache Maven, Java 8, Leadership, IT Strategy, Scrum, DevOps, REST APIs, API Integration
Senior Java Developer (Contract)
2014 - 2014
Bedside Clinical Systems
- Worked on the full stack of an application involving HL7 integration with hospitals, performance tuning, and DB optimization.
- Created several REST APIs and UI screens to manage admin configuration, vital signs, and patient weight data.
- Migrated a web application (including HL7 integration) from PostgreSQL to Microsoft SQL Server.
- Optimized DB queries to ensure the return of HTTP requests within a second in a load test environment.
- Updated online vital sign charts with custom components using SVG and D3.js.
Technologies: JavaScript, CSS, Bootstrap, REST, Apache Tomcat, HL7, SQL, Hibernate, Spring MVC, Java, HTML, Agile Software Development, Unit Testing, Continuous Integration (CI), Apache Maven, Java 8, Spring, Scrum, Full-stack, REST APIs
Senior Java Developer (Contract)
2012 - 2013
QuickPlay Media
- Built and maintained several modules of the video processing platform to download, transcode, encrypt, package, and publish video content.
- Created and maintained several workflow components tying together the module of a video processing platform.
- Built and maintained a REST API for managing the workflow of the video processing platform.
- Optimized performance of MongoDB queries to ensure they execute fast.
- Designed integration of the application with a reporting server.
Technologies: Apache Maven, Shell Scripting, JUnit, MongoDB, Spring MVC, REST, Apache Tomcat, Java, Continuous Integration (CI)
Experience
STCKD App
https://apps.apple.com/us/app/stckd/id1593378634• Hired a staff iOS developer (freelance) and an intermediate iOS developer (part-time).
• Transformed the prototype built by an agency into a production-grade mobile app, and its back-end endpoints were built in AWS.
• Designed, built, and maintained back-end endpoints.
• Led technical implementation of new features, including OCR scanning of shoe box labels in order to extract shoe details, ability to follow other users, public/private profiles, email and push notifications, forums, etc.
• Transformed the prototype built by an agency into a production-grade mobile app, and its back-end endpoints were built in AWS.
• Designed, built, and maintained back-end endpoints.
• Led technical implementation of new features, including OCR scanning of shoe box labels in order to extract shoe details, ability to follow other users, public/private profiles, email and push notifications, forums, etc.
LinkedIn Profile Optimizer AI Agent
An AI Agent that provides personalized recommendations on optimizing the user's LinkedIn Profile. It was created using the free low-code https://agent.ai platform.
Key skills: Claude Sonnet 3.7, agent.ai, LinkedIn API
Key skills: Claude Sonnet 3.7, agent.ai, LinkedIn API
Stage My Dream Home
An AI-powered virtual staging platform. I developed an innovative website called "Stage My Dream Home," which leverages generative AI to transform ordinary room photos into beautifully staged spaces in various styles such as modern, classic, and minimalist.
PROBLEM
The project addressed the challenge for realtors to stage empty rooms and create stunning photos of a property while the previous owner/tenant is still living and the property is still cluttered. Traditional staging and post-processing photos are costly and time-consuming, and a more efficient solution was needed.
MY CONTRIBUTIONS
I led the project from concept to completion, utilizing my front-end, back-end, cloud infrastructure, and AI skills.
OUTCOMES
The platform significantly reduced staging costs and time, offering realtors a seamless user experience for creating digitally staged images in a few clicks.
PROBLEM
The project addressed the challenge for realtors to stage empty rooms and create stunning photos of a property while the previous owner/tenant is still living and the property is still cluttered. Traditional staging and post-processing photos are costly and time-consuming, and a more efficient solution was needed.
MY CONTRIBUTIONS
I led the project from concept to completion, utilizing my front-end, back-end, cloud infrastructure, and AI skills.
OUTCOMES
The platform significantly reduced staging costs and time, offering realtors a seamless user experience for creating digitally staged images in a few clicks.
Demo Phone Bot Using OpenAI Realtime API and Twilio
https://github.com/davidkiss/openai-twilio-phonebot-demoThis is a simple demo on how to use the OpenAI Realtime API with Twilio to create a phone bot that can accept incoming phone calls and use OpenAI to generate responses in real time.
Key technologies: OpenAI Realtime API, Twilio Voice, TypeScript, Node.js, Express.js, Websockets, Ngrok
Key technologies: OpenAI Realtime API, Twilio Voice, TypeScript, Node.js, Express.js, Websockets, Ngrok
Appointment Booking Chatbot
https://github.com/davidkiss/langchain-appointment-booking-demoAppointment booking chatbot integration with Google Calendar
I developed a demo chatbot application that utilizes Python, Langchain, MCP, Pipedream, and the Google Calendar API. The project showcases the integration of an appointment booking chatbot with third-party services, specifically Google Calendar, using the Model Context Protocol (MCP) in Langchain.
PROBLEM
The project addressed the challenge of seamlessly integrating chatbots with external services like Google Calendar to automate appointment scheduling and management.
OUTCOMES
The integration successfully automated appointment scheduling, reduced manual input, and streamlined user interactions with Google Calendar. This enhanced user experience demonstrated the potential for broader applications in various service industries.
I developed a demo chatbot application that utilizes Python, Langchain, MCP, Pipedream, and the Google Calendar API. The project showcases the integration of an appointment booking chatbot with third-party services, specifically Google Calendar, using the Model Context Protocol (MCP) in Langchain.
PROBLEM
The project addressed the challenge of seamlessly integrating chatbots with external services like Google Calendar to automate appointment scheduling and management.
OUTCOMES
The integration successfully automated appointment scheduling, reduced manual input, and streamlined user interactions with Google Calendar. This enhanced user experience demonstrated the potential for broader applications in various service industries.
FastAPI Hotel Booking Demo
https://github.com/davidkiss/fastapi-playwright-demoCreated a demo FastAPI application that fetches hotels by city from Booking.com using Playwright, an open-source browser automation library. The project involved setting up a virtual environment, fetching dependencies, and installing the Chromium browser for Playwright. The application was designed to run on a local server using Uvicorn.
Key skills: Python, FastAPI, Playwright
Key skills: Python, FastAPI, Playwright
LangGraph Multi-agent Customer Support Chatbot Demo
https://github.com/davidkiss/langgraph-multiagent-demoA demo multi-agent chatbot system built for a fictitious Maple Ridge Mortgages company using Python, LangGraph, LangChain, ChatGPT, RAG, and FAISS.
It showcases the common building blocks of Agentic AI:
• RAG (using FAISS)
• Input and output guardrails
• Human in the loop
• Tools - Gmail for sending notification emails and Google Calendar for managing appointments
• Multiple agents with their own responsibilities, including a supervisor, an FAQ agent, a messaging agent, and a calendar agent
• Tracing using LangSmith
It showcases the common building blocks of Agentic AI:
• RAG (using FAISS)
• Input and output guardrails
• Human in the loop
• Tools - Gmail for sending notification emails and Google Calendar for managing appointments
• Multiple agents with their own responsibilities, including a supervisor, an FAQ agent, a messaging agent, and a calendar agent
• Tracing using LangSmith
Outbound Appointment Scheduling Voice AI
https://github.com/davidkiss/appointment-booking-agent-outbound-demoCreated a demo FastAPI application that integrates with Vapi.ai to make outbound calls to patients and schedule their appointments using a Google Calendar MCP server. This project involved setting up a seamless interaction between AI models and external data sources using the Model Context Protocol (MCP).
Key skills: Python, FastAPI, Vapi.ai, ChatGPT, MCP, Google Calendar
Key skills: Python, FastAPI, Vapi.ai, ChatGPT, MCP, Google Calendar
LangGraph Chatbot with FastAPI MCP Server
https://github.com/davidkiss/langgraph-fastapi-mcp-server-demoBuilt this sample project that involved transforming a shopping list application using FastAPI into a Model Context Protocol (MCP) tool for a LangGraph chatbot. The project aimed to enable seamless interaction between AI models and the shopping list application, allowing users to manage their shopping lists via chat.
Key skills: Python, FastAPI, LangChain, LangGraph, ChatGPT, MCP
Key skills: Python, FastAPI, LangChain, LangGraph, ChatGPT, MCP
PDF Extract Chatbot Demo
https://github.com/davidkiss/langchain-pdf-table-extractA sample LangChain based chatbot where users can upload PDF files and ask questions about the PDF's content, including tables.
It uses LangChain's PyMuPDF4LLMLoader to extract text from a PDF file and enriches it with tables extracted using the img2table library.
It uses LangChain's PyMuPDF4LLMLoader to extract text from a PDF file and enriches it with tables extracted using the img2table library.
Sample LLM as a Judge Evaluator for RAG Chatbot
https://github.com/davidkiss/langgraph-evaluator-demoA sample LLM is used as a judge evaluator to test an AI Agent that can answer questions from an FAQ using LangChain, LangGraph, LangSmith, ChatGPT, OpenEvals, and Pytest. This project aims to show quantitative ways to measure the performance of LLM applications.
WhatsApp Chatbot for Eralpcaner.org
This is a WhatsApp customer service and lead generation chatbot for eralpcaner.org that answers users' questions using RAG in English and Turkish and uses call-to-action questions to guide users to the next step in the conversation.
Key skills: n8n, ChatGPT, Pinecone, RAG, tools
Key skills: n8n, ChatGPT, Pinecone, RAG, tools
Education
1997 - 2003
Master's Degree in Computer Science
Budapest University of Technology and Economics - Budapest, Hungary
Skills
Libraries/APIs
REST APIs, Node.js, Java Message Service (JMS), Vue, LinkedIn API, React, Pandas, Drizzle, Google Calendar API, Playwright, Gmail API, OpenAI API
Tools
Apache Maven, IntelliJ IDEA, Apache Tomcat, Git, Jenkins, Gradle, Helm, AWS CloudFormation, GitHub, ChatGPT, Claude, AWS Step Functions, AWS Cloud Development Kit (CDK), Amazon Cognito, Expo, Shadcn, n8n
Languages
Java, JavaScript, SQL, Python, HTML, CSS, Groovy, Java 8, TypeScript, Java 9, GraphQL, Python 3
Frameworks
Spring Boot, Spring MVC, Spring, JUnit, Bootstrap, Apache Camel, Hibernate, Spring Security, Angular, Grails, Serverless Framework, Django, MUI CSS, Express.js, React Native, Next.js, Tailwind CSS, Material UI, LangGraph
Paradigms
Microservices, DevOps, REST, Test-driven Development (TDD), Continuous Integration (CI), Agile Software Development, Scrum, Unit Testing, HL7 FHIR Standard, Model Context Protocol (MCP), Automation
Platforms
Amazon Web Services (AWS), Docker, Firebase, MacOS, Linux, Android, Oracle, OpenShift, Kubernetes, Visual Studio Code (VS Code), Azure, AWS Lambda, Google Cloud Platform (GCP), Twilio, LangSmith
Storage
MongoDB, Google Cloud, NoSQL, MySQL, PostgreSQL, Hazelcast, Amazon S3 (AWS S3), Cloud Firestore, Amazon Aurora, Azure Cosmos DB, Data Pipelines, Amazon DynamoDB
Other
APIs, Architecture, Startups, Full-stack, HL7, Shell Scripting, Cloud, OAuth, Lean Development, IT Strategy, Leadership, Strategic Planning, Software Development, LivePerson, Artificial Intelligence (AI), LangChain, FastAPI, ChatGPT API, ChatGPT Prompts, Groq, Meta Llama, Deepgram, GitHub Actions, Vector Search, Llama 3, Gemini, Serverless, Gemini API, Generative Artificial Intelligence (GenAI), Supabase Auth, Full-stack Development, API Integration, OpenAI, AI Agents, LinkedIn Profiles, Large Language Models (LLMs), Supabase, Cursor AI, WebSockets, Agentic AI, Retrieval-augmented Generation (RAG), FAISS, vapi.ai, AI Chatbots, PDF Scraping, Prompt Engineering, CI/CD Pipelines, Pinecone, Vector Databases
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