# Senior Software Engineer - Encryption & PHI

**Company:** [StackAI](https://hotfix.jobs/companies/stackai)
**Location:** San Francisco, CA, New York, NY
**Role:** Backend Engineering
**Salary:** $248k – $282k/yr
**Experience:** 5+ years
**Skills:** Python, Applied Cryptography, Encryption, Key Management, Authentication, Token Infrastructure, Multi-Tenant Isolation, Phi, Pii, Hashicorp Vault, Cloud Kms, Hsms, Pki, Cryptographic Signing
**Posted:** 2026-09-02

> Build and operate backend security systems for encryption, key management, sensitive data, credentials, tenant isolation, and authentication. Requires strong production Python experience, applied cryptography knowledge, and at least 4 years building security-critical systems.

## Job Description

## Responsibilities
- Design and evolve encryption and key-management systems, including key scoping and rotation across hosted, VPC, and on-premises deployments.
- Build controls to detect, transform, and safely handle PHI, PII, and other sensitive data across workflows, connectors, model calls, logs, and storage.
- Secure customer-provided credentials and tokens from storage and access control through runtime use.
- Improve tenant isolation, signing and verification, session and token handling, and service-to-service authentication.
- Build shared Python services, libraries, and APIs for consistent security-critical behavior.
- Plan and execute migrations, compatibility periods, staged rollouts, observability, recovery, and rollback for live systems.

## Requirements
- 4+ years of experience building and operating production backend systems.
- Strong professional experience with Python in a substantial production codebase.
- Hands-on experience implementing and operating security-critical product systems.
- Depth in at least one area such as encryption and key management, authentication and token infrastructure, multi-tenant isolation, sensitive-data processing, or secure credential storage and runtime use.
- Practical knowledge of applied cryptography.
- Experience changing critical systems without disrupting existing customers or making previously stored data inaccessible.
- Strong judgment around trust boundaries, failure modes, and consequences of compromise.
- Ability to take ambiguous technical problems from investigation through production rollout.

## Nice-to-haves
- HashiCorp Vault, cloud KMS products, HSMs, envelope encryption, or key rotation.
- PHI or PII detection, redaction, pseudonymization, or tokenization.
- PKI, certificate systems, or cryptographic signing.
- Multi-tenant SaaS products handling sensitive customer data.
- Healthcare, payments, identity, financial infrastructure, or other security-sensitive domain experience.
- Self-hosted, VPC, on-premises, or air-gapped deployments.
- AI-agent, LLM, or connector-based application architecture.
- Startup or growth-stage product experience.

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