
Gabriel Breahna
Verified Expert in Engineering
Data Engineering Developer
Bucharest, Romania
Toptal member since September 15, 2022
Gabriel is a software engineer with 20+ years of experience in mission-critical SQL/NoSQL/cloud databases. He’s built large-scale OLTP systems and data warehouses exceeding 10TB, tuned queries on 10+ billion row tables, led greenfield builds, modernizations, and mergers. Gabriel is an Oracle, PostgreSQL, Snowflake, BigQuery, Redshift, and Databricks expert. He delivers architectural vision, deep performance tuning, and production-grade reliability across cloud, hybrid, and on-prem systems.
Portfolio
Experience
- Databases - 20 years
- SQL - 20 years
- Data Warehousing - 15 years
- Data Integration - 15 years
- Data Analytics - 15 years
- SQL Performance - 15 years
- Big Data - 10 years
- Data Engineering - 10 years
Availability
Preferred Environment
SQL, Data Warehousing, Data Analytics, Big Data, Databases, Data Engineering, SQL Performance, Data Integration, Business Intelligence (BI), Back-end
The most amazing...
...thing I've done was rescue a client’s crypto PostgreSQL database stuck at 100% CPU. I rewrote ORM SQL, added logging, and cut load to 20%.
Work Experience
Principal Software Developer
Oracle Corporation
- Migrated 100+ apps from on-premise to Oracle Cloud, then to Autonomous Database, improving scalability, automation, and reducing operational overhead.
- Modernized HR apps acquired by Oracle—integrated or replaced them with scalable, unified solutions adopted across internal teams.
- Built recruiting tools internally adopted at Oracle; later integrated into the core Oracle HR product by enterprise engineering teams.
- Developed a candidate scheduling app integrated with Oracle HCM Cloud, Microsoft Graph, Zoom, and Slack via RESTful APIs.
- Built RESTful APIs for internal services using ORDS and OAuth2 to expose tables, procedures, and schemas to various teams and tools.
- Improved interviewer feedback collection by integrating LLMs to guide and structure insights from technical and behavioral evaluations.
- Implemented AI-powered impersonation detection using face recognition and biometric checks to prevent candidate fraud.
- Built sentiment analysis pipelines to extract meaning from candidate polling responses, improving HR decision-making.
- Tuned critical SQL queries and optimized PL/SQL routines, reducing query times and resource usage across several Oracle-based systems.
Software Engineer | Data Engineer
Freelance Clients
- Created batch-and-streaming Google Cloud Dataflow pipelines/DAG to insert data from 4,000+ IoT devices into a 10TB Goole BigQuery data warehouse. Used GCP console and Python for the job and extracted data via BigQuery and SQL.
- Refactored a GPS tracking application from Oracle RDBMS, Oracle APEX, and GlassFish to an open-source solution based on PostgreSQL, Python, Bootstrap, and OpenStreetMap tiles. Used SQL, Python, Flask, Bootstrap, HTML, CSS, JavaScript, and Leaflet.
- Migrated a GPS tracking application hosting 2,000+ GPS devices from an Oracle RDBMS-based solution to an open-source solution based on Traccar Java-based application and PostgreSQL RDBMS.
- Migrated a data center from on-premise to OVHcloud bare-metal servers, Linux, Apache Tomcat, GlassFish, NGINX, Oracle RDBMS, Oracle APEX, PostgreSQL, and Python. Provisioned Linux boxes. Installed and configurated Linux and Oracle RDBMS.
- Architected the solution, created ETL pipelines, and developed SQL code for 10TB of data generated at a Euro 6 emission test time. Used GCP BigQuery, Dataflow, Apache Beam, streaming/batch pipeline, Pub/Sub, Cloud Functions, and Cloud Storage.
- Developed a GPS tracking device, including the firmware using C and the integration into the Traccar app. It was manufactured at PCBWay.com at a very affordable price. Used STM32F4 microcontroller, STM32CubeMX, and KiCad.
- Built a 6DOF robotic arm using mechanical parts from a Borunte robot and added new Inovance servo drivers. Used SOEM open source, extending it using real-time C programming. Created a ROS control driver and MoveIt trajectory control.
- Localized the Odoo/OpenERP for the Romanian market, which included building modules, reports, and enhanced forms. Sold the service as a SaaS. Used Python, Selenium, PostgreSQL, SQL, Docker, and OVHcloud.
- Developed a data warehouse for a Romanian holding to consolidate its operations from distribution, manufacturing, wholesale, and retail, from multiple ERPs inherited after multiple acquisitions, using Azure, Synapse, Data Factory, and PowerBI.
- Conducted multiple one- to six-month-long freelance projects as a software and data engineer using a wide range of technologies such as AWS, Azure, GCP, Snowflake, Redshift, PostgreSQL, MySQL, Airflow, Python, Lambda, Kafka, CDC, dbt, EKS, and MKS.
Database Engineer
Builders Ltd.
- Fixed the AWS RDS PostgreSQL performance issue, lowering it from 100% to 30%, reducing execution time from minutes to under one second.
- Enhanced the back-end app (Node.js/TypeScript) to deal with mint/burnt tokens.
- Upgraded FTSO Flare/Songbird FTSO apps (Node.js/TypeScript) to the latest ccxt library and fixed miscellaneous bugs along the process. Streamed all recorded data into BigQuery for later ML processing.
Software Engineer | Data Engineer
Euro Bit SA
- Implemented Oracle EBS 12.2 financials, order management, procurement, supply chain planning, and manufacturing.
- Served as an app admin, DBA, and SQL developer, which included SQL performance/tuning and management, developing SQL and PL/SQL customizations and reports.
- Built a vehicle spare parts webshop tightly integrated with Oracle EBS R12. Used Oracle RDBMS, Oracle APEX, ORDS, HTML, JavaScript, CSS, and jQuery. Integrated it also with TecDoc via RESTful API and OAuth2.
- Led the build of a SaaS model GPS vehicle-tracking app and used Oracle RDBMS, Oracle APEX, HTML, CSS, JavaScript, LeafletJS, jqPlot, Apache Tomcat, and OpenStreetMap. It oversaw 10,000+ GPS units, 10TB of data, and 20 billion records at its peak.
- Crafted a customized putaway and picking algorithm for the Oracle EBS WMS and MSCA module. Used SQL, PL/SQL, and Java. WMS was used to manage a 500,000-square-foot warehouse, and the algorithm increased overall efficiency by 10%.
- Constructed a customized EDI integration module for Oracle EBS order management, shipping, and purchasing. Used SQL, PL/SQL, EDI, iDoc, XML, and JSON. At its peak, the system managed 5,000 orders/day and one million orders/year.
- Developed a driver for Datecs ECR to integrate it with Odoo/OpenERP. Used Qt.
- Made business intelligence dashboards and reports based on Oracle EBS data. Used SQL, Oracle OBIEE, and Weblogic.
- Developed 20+ Oracle EBS extensions using Oracle APIs, interfaces, SOA, XML, a RESTful API, APEX, SQL, PL/SQL, SQL Loader, and SFTP.
IT Manager | Project Manager | Developer
Euro Trade Invest SA
- Developed a tailored application for an alcohol plant from scratch and integrated it with SCADA and other sensors; used Oracle RDBMS, Borland Delphi, and C.
- Built an app for a chain of 16 duty-free shops using Orale Personal Edition and Borland Delphi.
- Constructed a fiscal printer driver with bidirectional communication with the main POS; used C and C++.
Software Engineer
TAROM SA
- Created new ETL pipelines and maintained existing pipelines for data coming from 30+ agencies abroad; used Borland C++.
- Integrated the Boeing Spare Parts electronic catalog with the airliner purchasing system using Borland C++.
- Cleaned up OTP Airport passengers' onboarding data and reused that data to generate the annual TAROM airliner timetable; it was done using Borland Delphi.
Software Engineer
ITC SA
- Developed a custom dispatching app for a small taxi company based on Oracle 7.3 and Borland C++.
- Oversaw and was responsible for software maintenance across the codebase. This required a wide understanding of the internals of the software and systems.
- Developed a custom app for the accounting department based on their ongoing specs using Visual FoxPro.
Experience
Software Consultancy
https://www.rudderstack.com/• Brought in under pressure to resolve major performance issues affecting RudderStack’s largest enterprise customers.
• Diagnosed core inefficiency: excessive query volume and unnecessary table copies in dynamic SQL pipelines, leading to 3–10× data amplification.
• Optimized SQL patterns across Snowflake, Redshift, BigQuery, and Databricks, significantly reducing transformation runtimes.
• Guided the team toward a scalable redesign with fewer intermediate steps and more efficient table generation logic.
• Collaborated with engineers to validate fixes and build confidence in the revised architecture.
• Established SQL performance tuning best practices tailored to the distinct characteristics of each cloud data warehouse.
Amazon RDS PostgreSQL Optimization
https://xhaven.ioDigital Analytics Tool Based on BigQuery and TypeScript
http://livedocs.comKEY CONTRIBUTIONS
• Architected and implemented incremental data ingestion pipelines, supporting append-only logic and minimizing duplication.
• Wrote advanced analytic SQL for BigQuery, enabling dynamic, user-defined reports across large datasets.
• Built custom Fivetran plugins in TypeScript to connect to non-standard data sources.
• Tuned PostgreSQL on Google Cloud Platform (GCP) for low-latency analytical workloads.
• Collaborated with the front-end lead and product owner to shape features and align API design with user needs.
• Helped deliver a platform where users could explore and visualize data in seconds, even at scale.
Digital Analytics Platform Based on Snowflake, BigQuery, Redshift, Databricks
KEY CONTRIBUTIONS
• Developed high-performance queries across Snowflake, Redshift, BigQuery, and Databricks to process 300+ million monthly events spanning three years.
• Applied SQL/JavaScript UDTFs, clustering, materialized views, and pre-aggregations to improve speed and reduce cloud compute costs.
• Created a custom Business Query Language (BQL) to abstract complex analytics logic, improving flexibility and front-end integration.
• Built a robust BQL-to-SQL transpiler using Go and ANTLR 4, supporting DynamoDB, PostgreSQL, and Amazon RDS.
• Engineered a scalable ingestion pipeline using Go, Python, AWS Lambda, Amazon EKS, RudderStack, and Segment, enabling real-time analytics and deep BI insights.
• Optimized cross-cloud data handling and orchestration using Amazon MSK and best practices for efficient, distributed processing.
Data Integration and Engineering Lead
KEY ACCOMPLISHMENTS
• Migrated heterogeneous databases into Redshift, designing unified schemas and ensuring data accuracy and integrity throughout each phase.
• Conducted extensive performance and scalability testing to validate production readiness and minimize risk.
• Built automated pipelines for both historical migration and real-time ingestion using AWS Lambda, Python, AWS Glue, Airflow, dbt, and CloudWatch Cron jobs.
• Standardized ETL/ELT workflows for long-term maintainability, cost efficiency, and data quality enforcement.
• Delivered a scalable analytics foundation enabling cross-domain insights and supporting critical business decisions.
Compressed Natural Gas 12.4 Liter Heavy-duty Engine EURO VI Emission Certifications
KEY ACCOMPLISHMENTS
• Built and managed a high-throughput data warehouse handling 10 TB of new data every two weeks, under strict timelines and certification requirements.
• Started with an on-prem Oracle-based warehouse, using SQL/PLSQL to design efficient ETL processes and execute extensive SQL tuning for high-performance queries.
• Migrated to Oracle Cloud Infrastructure (OCI) to modernize and scale the system, leveraging cloud-native tools to improve cost efficiency and reliability.
• Integrated Google Cloud and BigQuery, building Apache Beam DAGs to optimize ETL pipelines for performance, resilience, and scalability.
• Throughout the project, utilized and maintained pipelines across PostgreSQL, Snowflake, Oracle, and BigQuery, depending on evolving client and technical needs.
• Achieved EURO VI emissions certification based on the data platform's quality, speed, and reliability, highlighting its role in ensuring compliance, safety, and environmental performance.
Automotive Spare Parts Webshop
KEY CONTRIBUTIONS
• Integrated with Oracle EBS R12 to access real-time inventory, pricing, and sales order data.
• Developed RESTful APIs for express carrier shipping and automated replenishment with parts suppliers.
• Built custom RESTful microservices to support high-value customer workflows.
• Designed and implemented third-party integrations with insurance providers and major automotive manufacturers (e.g., Opel, Fiat, Jeep) via XML and JSON file exchange.
• Supported automation of price lists, requisitions, purchase orders, and sales orders through structured data pipelines.
• Leveraged Oracle RDBMS, APEX, ORDS, SQL/PLSQL, Docker Compose, and modern REST API patterns to deliver a robust, scalable system.
Oracle EBS Implementation, Personalization, Customization, Extension, Workflow, and Analytics
KEY ACCOMPLISHMENTS
• Developed Oracle EBS custom extensions using Oracle APEX to enhance functionality and improve user experience.
• Designed and implemented a custom data warehouse with mobile access apps, supporting operational and executive reporting.
• Integrated EBS with key accounts via EDI, enabling seamless B2B and B2C order flows.
• Built and integrated apps for express delivery, POS systems, and weighing scales, streamlining retail and fulfillment processes.
• Integrated EBS with packaging and bottling lines, conveyors (CANopen), and dock, yard, and fleet management systems, supporting industrial automation.
• Delivered business analytics solutions using Power BI and Tableau over Snowflake, BigQuery, Redshift, and Oracle ADW, unifying cloud and on-prem analytics.
Database Migration for a Fintech Company
KEY CONTRIBUTIONS
• Conducted in-depth analysis of existing schemas, stored procedures, triggers, and queries to plan and execute a compatible Oracle migration.
• Designed and implemented data type mappings and rewrote procedural logic to align with Oracle PL/SQL standards.
• Ensured data integrity and compatibility across platforms, performing rigorous testing and validation throughout the migration lifecycle.
• Evaluated both online and offline migration strategies to minimize production downtime.
• Delivered an SQL script–based migration approach with manual validation aligned with customer preferences for transparency and control.
• Performed query tuning and performance testing post-migration to ensure Oracle-side workloads met or exceeded previous performance.
Vehicle GPS Tracking SaaS Application
KEY ACCOMPLISHMENTS
• Originally built with Oracle APEX + Oracle RDBMS, later migrated to OVH Cloud and refactored using Python (Flask), PostgreSQL, and open-source tools.
• Integrated Traccar.org for GPS tracking and OpenStreetMap for mapping, geocoding, and reverse geocoding.
• Added support for IoT integrations, including temperature sensors in truck trailers and fixed asset tracking, enhancing fleet monitoring capabilities.
• Solved performance challenges over 20B+ records through advanced SQL optimization and scalable data architecture.
• Delivered reliable ingestion of high-frequency GPS + IoT events while maintaining real-time analytics and responsiveness.
• Maintained and evolved the platform for 15+ years, ensuring uptime, performance, and modern tech adoption.
External Candidate Database Scheduling Engine
KEY ACCOMPLISHMENTS
• Built a fully native PL/SQL scheduling system, eliminating the need for middleware by integrating directly with Microsoft Graph APIs for calendar, email, and attachments.
• Used UTL_HTTP, wallets, Cloud Vault, and OAuth2 pre-authentication to securely manage tokens and access secrets.
• Extended functionality with Zoom and Slack APIs, enabling automated meeting creation and cross-platform notifications.
• Solved high-scale performance issues related to scheduling and booking across tens of thousands of daily meetings.
• Delivered a robust and secure platform entirely within the Oracle ecosystem, proving its scalability and enterprise viability.
Custom Algorithms for an Oracle EBS 3PL Data Warehouse
The successful implementation made the end users happy, and the client could get contracts signed with all prominent players from the local market.
Open-source ERP and Odoo Romanian Localization
KEY ACCOMPLISHMENTS
• Built localized modules for XML-based receipts, Romanian VAT, invoices, and currency rate updates.
• Developed custom bill printers, ZPL2 label printing, and POS debranding features.
• Implemented Romanian-specific stock analysis, expiration tracking, and stock reports.
• Customized MRP cost calculations, key account SKUs, and related workflows.
• Used Python, XPath (QWeb), PostgreSQL, and SQL to deliver performant, maintainable solutions.
• Ensured all modules aligned with Romanian legislation and integrated smoothly into existing Odoo instances.
Education
Master of Science Degree in Industrial Engineering and Robotics
University Politehnica of Bucharest - Bucharest, Romania
Certifications
Cyber Security Auditor
Romanian Directorate for Cyber Security
Oracle Cloud Infrastructure Foundations 2020 Certified Associate
Oracle
PRINCE2 Practitioner
AXELOS
Skills
Libraries/APIs
REST APIs, ODBC, Graph API, Segment.io, PySpark, NumPy, Leaflet, Mapbox GL, Slack API, Node.js, QuickBooks API, Stripe API, Spotify API, GitHub API, Instagram API, X (formerly Twitter) API, Facebook API, YouTube API, LinkedIn API, Google API, Django ORM, SQLAlchemy, Pandas, Matplotlib, jQuery, jqPlot
Tools
AutoCAD, Oracle Application Express (APEX), Oracle Business Intelligence Enterprise Edition 11g (OBIEE), Git, Jira, Slack, Confluence, Zoom, Oracle Reports, Oracle E-Business Suite (EBS), BigQuery, Tableau, Microsoft Power BI, Microsoft Excel, Apache Airflow, Cron, ANTLR 4, AWS IAM, AWS CLI, AWS Key Management Service (KMS), AWS Glue, Microsoft Access, GitHub, RabbitMQ, pgAdmin, Looker, Spark SQL, MQTT, Sequelize, SSAS, GIS, Google Sheets, PyCharm, Apache Tomcat, Docker Compose, TecDoc, Odoo, Oracle SOA Suite, Kafka Streams, Power Query, Google Analytics, Amazon Athena, Amazon Elastic MapReduce (EMR), VMware, Data Guard, Microsoft Power Apps, Sage 300 SDK, VMware vSphere, Azure IoT Suite, Autodesk Fusion 360, MATLAB, Apache, Jenkins, Cloud Dataflow, Apache Beam, Plotly, EtherCAT, Altium Designer (PCAD), KiCad, Terraform, Ansible, NGINX, cURL Command Line Tool, Postman, Amazon EKS, SAP S/4HANA, Amazon CloudWatch, Relux, SOLIDWORKS
Languages
SQL, Python, JavaScript, Snowflake, Stored Procedure, T-SQL (Transact-SQL), C, C++, Java, Bash, Go, C#, C#.NET, Simulink, Pascal, HTML, CSS, XML, XPath, XQuery, XSLT, GraphQL, Scala
Frameworks
OAuth 2, Flask, JSON Web Tokens (JWT), Django, Apache Spark, Django REST Framework, Oracle JavaScript Extension Toolkit (JET), Qt, Selenium, QWeb, Spark, Hadoop
Paradigms
ETL, Business Intelligence (BI), Dimensional Modeling, B2B, Oracle Database Architecture, Database Design, Database Development, Automation, Microservices, ETL Implementation & Design, REST, OLAP, Agile, DevOps
Platforms
Docker, Linux, Oracle Database, Oracle, Google Cloud Platform (GCP), Azure, Amazon Web Services (AWS), AWS Lambda, Unix, Databricks, Mixpanel, AWS IoT, Debian, Solaris, OpenERP, Windows, MacOS, Oracle Cloud Infrastructure (OCI), Apache Kafka, Kubernetes, Microsoft Power Automate, Amazon EC2, Azure SQL Data Warehouse, X (formerly Twitter), Raspberry Pi, Dedicated SQL Pool (formerly SQL DW), Arduino, Blockchain Platforms, Firebase, Salesforce
Storage
PL/SQL, Oracle RDBMS, PostgreSQL, SQL Performance, JSON, MySQL, Oracle SQL, Oracle PL/SQL, SQL Loader, RDBMS, Databases, Data Pipelines, Microsoft SQL Server, Database Security, Relational Databases, Redshift, Database Architecture, SQL Stored Procedures, Amazon S3 (AWS S3), Oracle 10g, Database Structure, Database Transactions, OLTP, Database Performance, SQL Triggers, MySQL Server, Oracle DBA, Data Integration, Oracle 11g, Database Administration (DBA), Database Modeling, Database Migration, Google Cloud, Master Data Management (MDM), Database Lifecycle Management (DLM), DB, Amazon Aurora, SQL Server Integration Services (SSIS), Oracle Cloud, Data Centers, SQLite, Nextcloud, SQL Server Analysis Services (SSAS), OVH, MariaDB, Column-oriented DBMS, Data Lakes, Docker Cloud, NoSQL, IIS SQL Server, MongoDB, Apache Hive, Amazon DynamoDB, Elasticsearch
Industry Expertise
Accounting
Other
Data Warehousing, Oracle EBS, Oracle Performance Tuning, IT Project Management, Data Warehouse Design, Electronic Data Interchange (EDI), Back-end Development, Google BigQuery, Oracle VM VirtualBox, Microsoft Graph API, Data Center Migration, Oracle Discoverer, Oracle REST Data Services (ORDS), Cloud, Software as a Service (SaaS), Migration, Data Engineering, APIs, Data Architecture, Data Modeling, Star Schema, Data Processing Automation, Data Processing, CSV, Data Analysis, Scripting, ETL Tools, Data Visualization, Amazon RDS, Consulting, Data Analytics, Data Cleaning, Borland Database Engine (BDE), Financial Modeling, Database Optimization, Consumer Packaged Goods (CPG), Query Optimization, Performance Tuning, Query Composition, Back-end, Analytics, Relational Database Design, XML for Analysis (XMLA), Database Schema Design, SaaS, Datasets, Data Cleansing, Data Profiling, Dashboards, Supply Chain, Data Reporting, Data Migration, BI Reporting, Business Services, Enterprise Resource Planning (ERP), API Design, Transactions, Geospatial Data, Big Data, Message Queues, Big Data Architecture, Data Transformation, Google Cloud Functions, Data, Azure Data Factory (ADF), Solution Architecture, Data Auditing, Industrial Internet of Things (IIoT), Monitoring, Technical Architecture, Ajax, Sourcing & Procurement, ELT, Process Automation, Pipelines, Architecture, Optical Character Recognition (OCR), Algorithms, Interactive Dashboards, Reports, Fivetran, MySQL DBA, Integration, Microsoft 365, Proof of Concept (POC), ETL Development, ETL Testing, Oracle Fusion Applications, Oracle Security Server, Identity & Access Management (IAM), Veeam, Backup & Recovery, Network Engineering, Software-defined WAN (SDWAN), Data Center Infrastructure, Networking, Performance Optimization, Leadership, ETL Pipelines, eCommerce, Business to Business (B2B), Delta Lake, SSH, Cloud Migration, Geospatial Analytics, User Journeys, Web Marketing, IoT Protocols, Internet of Things (IoT), TCP/IP, API Integration, WebSockets, Business Requirements, Data Center Management, J1939, Data Flows, Distributed Systems, Startups, Scalability, Git Repo, Static Analysis, Shell Scripting, Google Pub/Sub, Machine Learning, Oracle Apps, Data Classification, Technical Leadership, Microsoft Data Transformation Services (now SSIS), Amazon Redshift, Debugging, IT Support, Reporting, Troubleshooting, Oracle HCM Cloud, OpenStreetMap, GlassFish, Data Encryption, Slack App, Oracle WebLogic Application Server, SFTP, Relational Data Mapping, User Experience (UX), Mobile Analytics, Financial Data, Robotic Process Automation (RPA), Data Governance, CI/CD Pipelines, DAX, Search, Networks, Streaming Data, Google Analytics 4, Spotify, TikTok, Azure IoT Edge, ESP32, CIM, LoRa, LoRaWAN, Microcontrollers, Excel 365, SCADA, Nominatim, Modbus Protocol, RS-232, RS485, Directed Acrylic Graphs (DAG), Arduino IDE, STM32CubeMX, Robot Operating System (ROS), SAP IDoc, RESTful Microservices, EDIFACT, User Interface (UI), Data Science, Data Build Tool (dbt), Amazon Marketing Services (AMS), Customer Data Platform (CDP), Change Data Capture, Segment, SAP, Digital Manufacturing, Real Estate, IT Audits, Audits, Profiling, Smart City Technology, Industry 4.0, HadoopXML
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