# Patrick Grennan

> Principal Software Engineer at Amazon Health Services

Location: San Francisco Bay Area, United States
Profile: https://flows.cv/patrickgrennan

## Work Experience
### Principal Software Engineer @ Amazon
Jan 2023 – Present | San Francisco, CA
Rejoined One Medical in July 2023 post-acquisition by Amazon.

I support the shared health technology and platform org spanning One Medical and Amazon Pharmacy.

### Software Engineer @ Gem
Jan 2022 – Jan 2023 | San Francisco Bay Area
I led long range strategy and execution for our backend platform and infrastructure. I also led a number of related company-wide initiatives:
* Designed and led implementation of our global permissions framework
* Designed and led implementation of a complete overhaul of our backend testing framework and processes
* Designed and implemented our infrastructure review process, leading to 60% savings of our AWS bill
* Designed and implemented our realtime elasticsearch syncing framework

Technologies:
Languages: Python, Typescript
Frameworks: Flask, React
Data Storage: Postgres, Elasticsearch

### Senior Staff Software Engineer @ One Medical
Jan 2021 – Jan 2021
I most recently was the tech lead for our data platform. I also led our Engineering Strategy group of Staff and above engineers, which directs the long-term architectural vision of our software at One Medical. I was One Medical's first Data Scientist / Engineer.

I architected and bootstrapped development of nearly all of our major data-related systems, including:
* Our data lake and data warehousing infrastructure
* Our data interoperability systems (how we exchange and reconcile data with other health systems using healthcare data standards like HL7, C-CDA, and FHIR)
* Our analytics toolkit (tooling for our analysts, data scientists, and ML engineers)
* Our data platform (a high-performance source-of-truth API service for clinical data and a foundational microservice)

Technologies that I worked with included:
* Languages: Python, Ruby, Golang, Typescript
* Frontend Frameworks: React, Angular
* Web Frameworks: Ruby on Rails, FastAPI
* DevOps and Services: Terraform, AWS ECS, Auth0, Docker
* Data Processing: Pig, Airflow, Spark, dbt, pandas
* Data Storage: MySQL, Redis, DynamoDB, Elasticsearch, AWS EMR, Snowflake

### Staff Software Engineer @ One Medical
Jan 2019 – Jan 2021 | San Francisco Bay Area

### Senior Software Engineer @ One Medical
Jan 2016 – Jan 2019 | San Francisco Bay Area

### Data Scientist / Data Engineer @ One Medical
Jan 2014 – Jan 2016 | San Francisco Bay Area

### Data Science Mentor @ Springboard
Jan 2015 – Jan 2018
I was a part-time mentor for Springboard's Data Science and Business Analytics courses.

### Data Scientist / Software Engineer @ Sparked.com
Jan 2012 – Jan 2014
Working as the lead of the Data Science platform of Sparked, I led the development and strategy of our data science/machine learning products and recommendation engine (which I was awarded a patent for). 

I worked on data from end to end - from data collection via a javascript tracking pixel, to large scale ETL, processing and aggregation workflows in hadoop, spark, and storm, to feature extraction, machine learning and visualization.

Technologies that I worked with included:
* Languages: Python, PHP
* Web Frameworks: Flask, Zend
* DevOps and Services: Puppet, Docker
* ML/DS: scikit-learn, pandas


## Education
### Bachelor of Arts in Individualized Study in Computational Thought / Artificial Intelligence
New York University

### Fordham University


## Contact & Social
- LinkedIn: https://linkedin.com/in/grennan
- Website: http://www.github.com/ptg180

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Source: https://flows.cv/patrickgrennan
JSON Resume: https://flows.cv/patrickgrennan/resume.json
Last updated: 2026-04-01