Catalin Oancea
Verified Expert in Engineering
Full-stack Developer
Bucharest, Romania
Toptal member since May 17, 2019
Catalin has over 13 years of experience developing web services using various languages at top companies such as Facebook, Bloomberg, Bolt, and Fitbit. As a production engineer at Facebook, he uses his site reliability engineering skills to design and build production-ready services that scale. Catalin has worked mostly in fast-paced teams distributed around the globe, where he has proven to be an excellent communicator.
Portfolio
Experience
- Data Structures - 10 years
- Node.js - 7 years
- Python - 6 years
- MySQL - 5 years
- Team Leadership - 4 years
- Distributed Systems - 4 years
- Machine Learning - 4 years
- People Management - 2 years
Preferred Environment
Visual Studio Code (VS Code), PyCharm, IntelliJ IDEA, Git, MacOS, Linux
The most amazing...
...project I've handled was a coding platform designed to sandbox executables and grade submissions from people preparing for their technical interviews.
Work Experience
People-managing Technical Lead
Bolt
- Developed the public API used by restaurants, stores, and shops to integrate directly with Bolt Food. They can now automate the menu (product catalog) and stock updates, and manage orders via a push/pull system.
- Created WMS integrations, POS integrations, and order management integrations with key vendors/restaurants (McDonald's and other big restaurant chains) that were scaled in multiple countries.
- Improved the menu system by adding different optimizations and validations. Introduced a sync mechanism between an SQL menu database and an instance of Elasticsearch. The sync is event-based and uses Amazon SNS and Amazon SQS.
- Managed a team of engineers that worked on the public restaurant API.
AI Engineer
Bloomberg LP
- Contributed to the AI search and relevance group, creating a new algorithm for time-aware named entity disambiguation. The search engine takes into account the world context when performing disambiguation and provides accurate suggestions.
- Worked on the research part for a few weeks. The research involved analyzing huge amounts of data using Spark and Hadoop to collect ambiguous search queries. It returned a few results to design a new model to fix this.
- Created a new model that significantly improved the accuracy of query interpretations, from 20% to 86%, in the cases where the query was ambiguous—for example, Amazon fire could be the Amazon product or the fire in the Amazon rain forests.
- Implemented the prediction function of the model in Python and deployed the newly implemented service in their beta environment, where monitoring and performance analysis were performed.
Software Engineer
Fitbit, Inc.
- Took part in the architecture review group for a Fitbit internal platform that exposes core Fitbit metrics, such as steps, calories, active minutes, etc., to other internal services.
- Designed and built large parts of this internal platform using technologies like Node.js, Cassandra, Kafka, Python, Bash, Thrift, and HTTP for communication.
- Worked on the development of this platform using mainly TypeScript and Node.js.
- Mentored two part-time engineers and helped them stay on track with their tasks while making sure they have plenty of new learning opportunities.
- Took part in the process of introducing Node.js in the company and helped developer productivity teams with boilerplate code and documentation to bring Node.js support on par with the existing languages that were in use in Fitbit.
Production Engineer
Facebook, Inc.
- Worked in the data center management and escalations team developing escalation tools.
- Used Python, Hack, Thrift, and React to develop a manual escalation tool—back end plus admin dashboard.
- Improved the usability of their existing tools and automated some escalation procedures.
- Created a management system to add on-call teams and rotations that worked as a provider system for the escalation service.
- Took part in design meetings and discussed ideas about performance improvements and scalability.
Software Engineer
Bookster
- Took part in the development of a recommender system. Used Apache Mahout and Java to implement complex machine learning algorithms.
- Developed back-end tools in C# for providing business people with consumer insights.
- Took part in the service language migration process, migrating code written in PHP to C#.
- Improved the admin dashboard by replacing jQuery with AngularJS.
- Created an internal calendar-like tool used by employees and by the management to request and approve time off.
Experience
Bolt Food Public API
I created WMS, POS, and order management integrations with key vendors and restaurants (including McDonald's and other major chains) that were scaled across multiple countries.
The public API is used by thousands of restaurants across tens of countries.
Bloomberg News Search Query Disambiguation
https://www.youtube.com/watch?v=ZyOcrzFsb00Bloomberg customers (businesses, governments, philanthropic organizations, etc.) conduct millions of news searches every day. They are looking for close to real-time news and information about companies and investment vehicles. Bloomberg's information retrieval and NLP systems help clients discover the right information they need.
AI Copilot for Exam Grading
https://vision-marker.comThe platform leverages advanced AI and machine learning to automate the marking process, providing accurate, consistent, and timely results for various questions across different subjects.
I created the public-facing API of the Co-Pilot. I used AWS Cloud technologies (CloudFormation, Lambda, API Gateway, SNS, SQS, Cognito, DynamoDB, S3, IAM), handled billing integration with Lago, refactored and debugged existing code, and created the documentation pipeline (Swagger).
Predictive Stock Modeling and Trading Strategy Optimization
KEY RESPONSIBILITIES
• Market Data Integration: Developed a robust simulator to pull minute-by-minute data for the most active stocks.
• Model Training: Implemented and trained predictive models in real-time, enabling intraday market reaction assessments and ensuring that trading strategies could adapt dynamically throughout the trading day.
• Ticker Symbol Recommendations: Provided real-time recommendations for ticker symbols, focusing on stocks expected to reach specific intraday performance thresholds.
OUTCOME
The market simulator successfully delivered real-time stock predictions and trading strategies, optimizing the decision-making process in high-frequency trading environments. This tool not only enhanced trading efficiency but also increased the potential for profit by accurately forecasting stock movements within short timeframes.
Precision Medicine AI Platform
https://www.insight-rx.comKEY RESPONSIBILITIES
• Python LLM Agent Development: Contributed to the development of a Python-based large language model (LLM) agent application, including seamless integrations with a web application, AWS S3 storage, and AWS SQS messaging service.
• Automated Testing: Developed comprehensive automated testing frameworks, integration tests, and end-to-end tests to ensure the reliability and robustness of the application.
Data Portal for Environmental Indicators
https://www.vizzuality.comThe portal is helping big companies around the world better understand how they can offset their carbon footprint and how to invest in green projects (either by conserving existing projects or by initiating new planting projects).
It also helps with viewing a cost breakdown for each big part of the project as well as the community benefits and carbon offsetting potential.
Education
Bachelor's Degree in Computer Science and Engineering
Politehnica University of Bucharest - Bucharest, Romania
Certifications
Improving Deep Neural Networks: Hyperparameter Tuning, Regularization and Optimization
deeplearning.ai
Structuring Machine Learning Projects
deeplearning.ai
Neural Networks and Deep Learning
deeplearning.ai
Advanced Python
Python - Data Analysis
Microsoft Technology Associate - Security
Microsoft
Microsoft Technology Associate - Database Administration
Microsoft
Skills
Libraries/APIs
Node.js, jQuery, Fitbit API, REST APIs, API Development, GitHub API, Pandas, NumPy, Google Sheets API, Intercom API, React, Socket.IO, Facebook API, Facebook Login, Facebook Ads API, Google APIs, Social Media APIs, AWS Amplify, Python Asyncio, Mahout, Segment.io, Google Maps, Google Maps API, Python API, SciPy, PySpark
Tools
Amazon Simple Email Service (SES), Pytest, Google Sheets, Jira, Moodle, Claude Code, Git, Notion, Microsoft Excel, Terraform, AWS Glue, Zapier, Celery, Subversion (SVN), IntelliJ IDEA, PyCharm, Apache ZooKeeper, Mesos, Apache Aurora, Apache Solr, Amazon Simple Notification Service (SNS), Amazon Simple Queue Service (SQS), Looker, Jupyter, Amazon Cognito, AWS CloudFormation, Amazon CloudWatch, AWS IAM, AWS Command Line Interface (CLI), Claude
Languages
TypeScript, Python, JavaScript, HTML, Go, SQL, XML, C#, Java, CSS, Pine Script, PHP, Hack, Bash, C++, JavaScript 5, JavaScript 6, Python 3
Frameworks
Express.js, Flask, Apache Thrift, Django, Next.js, Angular, Spark, Hadoop, Jest, NestJS, OAuth 2, AWS Serverless Application Model (SAM), Swagger
Paradigms
Agile Software Development, MEAN Stack, REST, Clean Architecture, API/Services Architecture, Database Design, Microservices, Agile, Unit Testing, Object-oriented Programming (OOP), ETL, CRUD, API Architecture, Parallel Programming, Design Patterns, Test-driven Development (TDD), DevOps, Automation, Management, Lambda Architecture
Platforms
Apache Kafka, Amazon Web Services (AWS), Mapbox, Harness, Google App Engine, Amazon EC2, Docker, Kubernetes, Vercel, Linux, MacOS, Mixpanel, Heroku, Visual Studio Code (VS Code), AWS Lambda, Jupyter Notebook, Azure, Blockchain, Google Cloud Platform (GCP), LangSmith
Storage
Amazon S3 (AWS S3), MySQL, Redshift, PostgreSQL, Database Architecture, NoSQL, Redis Cache, JSON, Data Pipelines, Elasticsearch, MongoDB, Cassandra, Amazon Aurora, PostGIS, Data Integration, HDFS, PostgreSQL 10, Amazon DynamoDB, Databases, Microsoft SQL Server
Other
Distributed Systems, Artificial Intelligence (AI), APIs, API Integration, Integration, Algorithms, Software Architecture, Back-end, Architecture, Web Services, Solution Architecture, Data Modeling, Cloud Services, Full-stack Development, Airtable, Full-stack, OAuth, Scalable Web Services, Document Parsing, Trading, CI/CD Pipelines, Large Language Models (LLMs), Finance, FastAPI, GeoJSON, WebGIS, Webhooks, CSV File Processing, HTTPS, Learning Management Systems (LMS), Module Integrations, Administration, Maintenance, Agentic AI, Vendor Management, Warehouse Management System (WMS), Consulting, Order Management, Intercom, Search, RAG Pipelines, SaaS, Open Banking, API Design, API Testing, Data, Large-scale Distributed Systems, Machine Learning, Neural Networks, Leadership, Team Leadership, People Management, Data Structures, Technical Leadership, Product Development, Serverless, Algorithmic Trading, Encryption, TradingView, Backtesting Trading Strategies, Data Extraction, Trading Bots, Data Engineering, Automated Trading Software, WebSockets, Financial Services, SOAP, HHVM, Apache Cassandra, Linkerd, A/B Testing, Maps, AWS DevOps, Health, Healthcare IT, Stock Trading, Stock Market, Stock Exchange, Stock Analysis, Deep Learning, Inventory Management, Inventory Management Systems, Amazon Fire TV, SDKs, Forums & Social Networking Portals, Lambda Functions, Billing, AI Model Integration, OpenAI GPT-4 API, Generative Pre-trained Transformers (GPT), Llama 2, OpenAI, Data Visualization, Data Analytics, Data Science, Alpha Vantage, Alpaca, Retrieval-augmented Generation (RAG), AIOps, AI Agents, LangChain, Llama 3, AdminJS
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