# Andrei Longhin

> Senior Software Engineer at Square

Location: London, England, United Kingdom
Profile: https://flows.cv/andreilonghin

Software Engineer with a track record of owning and shipping complex projects from 0 to 1, across startups and larger product-driven companies. Comfortable across the stack, with a bias for impact over process. Open-source contributor and enthusiastic user of AI tools to ship faster.

## Work Experience
### Senior Software Engineer @ Square
Jan 2023 – Present | Greater London
- Designed and built the Risk Controls platform from scratch, which became the golden path for freezing and unfreezing seller funds across Square; closed critical regulatory gaps while reducing churn by improving seller and agent experience; migrated >100 codepaths to the platform using Claude Code, cutting months from pre-AI estimates 

- Drove platform reliability and performance: reduced main service p99 latency from 500ms to 10ms, and halved infra costs from $12k to $6k/year via single-region migration 

- Became domain expert across Risk Controls, Square Card fraud evaluations (3DS and authorisations), and more; ramped up multiple team members through knowledge bases, runbooks, and regular knowledge-share sessions

### Software Engineer @ Stripe
Jan 2021 – Jan 2022 | London, England, United Kingdom
- Delivered plan for launching Stripe into a new market (identified market requirements, mapped to solutions, split into projects, created timelines & execution plan, onboarded other engineers, derisked and led initial execution)
- Was the first engineer of novel team targeting self-serve UX in specific markets: identified issues in onboarding process, designed solutions and executed, leading to 80% drop in user confusion (selecting "Not sure" in UI)
- Company building: mentor of 2 teammates, during 1 quarter I held more interviews than 97% of engineers at Stripe

### Senior Software Engineer @ Mimica Automation
Jan 2019 – Jan 2021 | London Area, United Kingdom
- Worked on a web application used to create and display different visualisations of processes and decide how fit they are for automation
- Led projects involving multiple engineers, notably a complete restructuring of the UI/UX for the main process visualisation tool, which led to the company's first successful client engagements
- Helped scale the web application to handle very large amounts of data (e.g by segmenting payloads of HTTP requests, leveraging browser cache etc.)
- Brought on multiple practices for reducing bugs and dev time (e.g unit and e2e testing, using typed languages, following well-known design patterns etc.)
- Mentored multiple colleagues to the extent that the team working on the web application grew from 2 to 8 people
- Made open-source contributions to Vis Network (graph visualisation library)

### Software Engineer @ AmberBox Gunshot Detection
Jan 2018 – Jan 2019 | London, United Kingdom
- Worked on multiple projects, notably created a user authentication and authorisation platform used by 3 different web applications
- Made open-source contributions to Californium (IoT networking library) and CodeceptJS (automated testing library)

### Software Engineering Intern; Junior Software Engineer @ Click Travel
Jan 2016 – Jan 2018 | Birmingham, United Kingdom
- Worked on an award-winning business travel platform, specifically on a web application used by tens of thousands of users to mass book hotels/trains/airplanes
- Devised an algorithm that masks card details from logs, which helped platform achieve PCI compliance
- Was promoted to regular employee after 1.5 months as an intern (worked during university)


## Education
### Bachelor of Science with Honours (B.Sc. Hons) in Computer Science
University of Birmingham

### Full Stack Web Developer Nanodegree in Web Development
Udacity


## Contact & Social
- LinkedIn: https://linkedin.com/in/aml2610
- GitHub: https://github.com/aml2610

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Source: https://flows.cv/andreilonghin
JSON Resume: https://flows.cv/andreilonghin/resume.json
Last updated: 2026-03-30