Staff Application Security Engineer

OverviewStaff Application Security Engineer at Ledn. Ledn is a global financial services company built for digital assets, helping to improve the everyday lives of Bitcoin holders while building generational wealth. We offer lending, savings and trading products to digital asset holders in over 150 countries. Our team is diverse and values integrity, ownership, progress, and empathy. This is a full-time role focused on strengthening the security of our Bitcoin-backed loan platform. Security is fundamental to protecting customers and the business, and this role will drive both tactical improvements and long-term strategy for securing applications and authentication systems. You will work across JavaScript/TypeScript services, AWS serverless stack (Lambda, API Gateway, Cognito, SNS, SQS), MongoDB and Kubernetes microservices, and will evolve our authentication layer toward modern, phishing-resistant approaches. You will also design and operate AWS Nitro Enclaves to protect critical data and cryptographic operations in isolated environments. This is a hands-on engineering role with direct impact on product security, infrastructure security, and customer trust. ResponsibilitiesApplication Security: Lead secure design and code reviews across engineering teams. Define and enforce secure coding practices for JavaScript/TypeScript services. Automate vulnerability detection (SAST, SCA, DAST) within CI/CD. Conduct threat modeling and risk assessments for new features. Partner with engineers to remediate vulnerabilities and improve secure development practices. Authentication & Identity: Own the roadmap for authentication and identity across customer and internal applications. Enhance Cognito-based identity architecture with stronger, phishing-resistant MFA solutions (e.g., WebAuthn, passkeys, hardware tokens). Collaborate with Product to align usability, compliance, and security in authentication flows. Define secure session management, device trust, and account recovery. Confidential Computing (AWS Nitro Enclaves): Design enclave-based architectures to isolate and protect sensitive workloads. Integrate Nitro Enclaves with KMS and secure APIs. Migrate high-value operations into enclave environments. Ensure compliance, auditability, and resilience of enclave workloads. Additional Security Domains: Harden AWS services with least-privilege IAM and secure key management. Improve Kubernetes security posture (RBAC, pod security, image scanning, runtime monitoring). Deploy and operate a SIEM framework; develop detection rules, dashboards, and incident playbooks. Support compliance initiatives (SOC 2, ISO 27001) with security controls and documentation. What You Bring To Ledn10 years minimum of proven experience in Application Security with a focus on web and cloud-native applications. Strong knowledge of JavaScript/TypeScript/Golang/Python and modern web vulnerabilities (OWASP Top 10, auth bypasses, business logic flaws). Expertise with AWS security best practices, particularly in serverless architectures. Hands-on experience with AWS Nitro Enclaves for confidential computing. Deep understanding of authentication and authorization standards (OAuth2, OIDC, WebAuthn, FIDO2). Practical experience with Cognito / Auth0 (MFA, custom flows, secure session handling). Background in SIEM design and log correlation across cloud and application layers. Familiarity with Kubernetes security (RBAC, pod security, admission controls, image scanning). Experience with Secure Code Review and understanding of software supply chain. Deep understanding of Linux internals. Remediate vulnerabilities identified in the penetration test report. Strong communication and collaboration skills to influence engineering and product teams. Nice To HaveFamiliarity with Bitcoin custody and key management practices. Knowledge of Infrastructure as Code security (Terraform, AWS CDK). Prior work on user-facing security features such as passwordless authentication, recovery flows, or device trust. Culture & Ideal CandidateWe are looking for a leader who thrives in startup or tech environments and embodies our values. The ideal candidate will be adaptable, resilient, and comfortable navigating ambiguity in a high-growth, fast-paced environment. They should have a builder’s mindset, be collaborative across functions, and demonstrate integrity and accountability in handling confidential information. Experience working in a remote environment is preferred. A Taste Of What We ProvideTremendous growth opportunities as one of the world’s leading digital asset companies. Comprehensive total rewards package starting on day one, including a competitive PTO package. Ownership in the company through equity; remote work flexibility up to 180 days worldwide (subject to restrictions). A purpose-driven career; we remove barriers so you love what you do. Equal opportunity employer; we value inclusivity and diversity. Accommodation requests are welcome at any stage of recruitment and will be addressed confidentially. Ledn Working Environment: Our team is global, remote-first, with presence in North America, Latin America, South Africa and Europe. Due to high volume of applications, only candidates who qualify will be contacted. Shortlisted candidates may be asked to submit a short video response and we may review publicly available social media activity relevant to the role. No agencies or recruiters please. We do not accept unsolicited agency resumes and we are not responsible for any fees related to unsolicited resumes. Seniority level: Mid-Senior level Employment type: Full-time Job function: Information Technology Industries: Retail Location: Cascavel, Paraná, Brazil (remote work allowed as described) #J-18808-Ljbffr