Security Engineer - AppSec

About the Team
Security Engineering is a small team that answers one question: was it built right? We run our own AI-driven red team against Rain's code and cloud, gate pull requests before they merge, and write the baselines that say how every system should be configured. Our blockchain work is covered. This role owns everything else: the backend services, APIs, cloud, and edge that move real money for real customers.

We work closely with Security Operations: we give them high-quality findings to coordinate fixes for, and clear configuration rules they can build detections on.

About the Team
Security Engineering makes sure Rain is built right. We run our own AI-driven red team against our code and cloud, gate pull requests before they merge, and set the baselines for how every system is configured. This role owns everything outside blockchain: the backend services, APIs, cloud, and edge that move real money. We give Security Operations high-quality findings to coordinate fixes for, and clear configuration rules to build detections on.

About the Role
You'll be Rain's application security expert and the quality bar for every non-chain finding we produce. The calls are yours: what's real, how bad it is, and what has to be fixed before launch. You'll hold the line with engineers when it matters, and make the case so they agree, not just comply.

What You'll Do
Review red team findings before they reach engineers: reproduce them, cut false positives, set severity, and write tickets clear enough to fix without a meeting. Improve the scoring that grades them

Harden our backend services and APIs, especially the money-moving paths. You'll often write the fix yourself

Own edge defenses: DDoS protection, rate limiting, WAF rules, and abuse controls

Write secure configuration baselines for our cloud, code, and SaaS, and turn them into automated checks

Grow our PR security gate so more bugs are blocked before merge

Own attack surface coverage, and run architecture reviews on new and high-risk systems

Find, test, and pick the best security tools, whether we buy, adopt, or build

What We're Looking For
4+ years in application security, product security, or security-minded backend engineering

You've owned security decisions. You can tell a senior engineer their design needs to change and keep a good working relationship

You can read an unfamiliar codebase (TypeScript/Node.js) and find the bug that matters, and you know a scary-sounding finding from a real one

Hands-on cloud security (ideally GCP), Terraform, and edge defenses like WAFs and rate limiting

Experience with threat models or architecture reviews. You've run tool bake-offs and dropped tools that didn't earn their cost

You'd rather ship a check than write a document, and you use AI tools heavily without trusting them blindly

Bonus Attributes
Fintech, payments, or card issuing background (PCI DSS a plus)

Pentest, bug bounty, or red team experience

Experience building security scanners, static analysis rules, or LLM-based review tools

If you have the background: AI security for our agents and agentic payments, or corporate security alongside IT