Freelance Backend Developer

Python / FastAPI | AWS Infrastructure, Security & Scalability | AI Platform
Engagement: Freelance / Independent Contractor
Location: Remote
Duration: Initial project-based engagement with potential extension
About the opportunity
Transmission is seeking an experienced, hands-on freelance AWS Cloud & Backend Engineer to support the next stage of development of our proprietary AI-powered marketing intelligence platform.
We are looking for a senior technical specialist to independently assess and strengthen the existing AWS infrastructure and backend architecture, ensure the platform is secure, stable and capable of supporting increased user adoption, and contribute directly to Phase 2 development.
This is not a greenfield development project. We need someone comfortable auditing, improving and extending an existing application.

Key responsibilities
1. AWS infrastructure and security assessment

• Review the current AWS staging and production architecture, configurations and deployments.
• Assess ECS/Fargate, networking, application load balancing, IAM, Cognito, S3, KMS and Secrets Manager.
• Evaluate environment isolation, permissions, authentication, authorization and data security.
• Identify potential vulnerabilities, misconfigurations, security gaps and infrastructure risks.
• Recommend and implement remediation, prioritizing critical issues before broader production rollout.
• Review AWS CloudFormation configurations and infrastructure deployment practices.

2. Production readiness, performance and scalability

• Evaluate the platform's readiness to support increased concurrent users and application workloads.
• Assess API performance, database connections, application resource utilization and scaling configurations.
• Conduct or support load and stress testing to identify performance bottlenecks.
• Review application logging, CloudWatch monitoring, alerting and incident-response capabilities.
• Evaluate backup, recovery, resilience and deployment/rollback processes.
• Ensure staging environments adequately represent production behavior.

3. Backend development and Phase 2 support

• Develop and improve backend functionality using Python and FastAPI.
• Troubleshoot and optimize REST APIs and third-party integrations.
• Support PostgreSQL, Snowflake and AWS-hosted data integrations.
• Develop reliable background processing, scheduled jobs and asynchronous workflows.
• Support integration of AI/LLM services with the existing application.
• Collaborate with our AI developer and data scientists to complete Phase 2 functionality.
• Document changes and provide technical knowledge transfer.

Required technical qualifications

• 7+ years of software engineering experience, including senior-level backend development.
• Extensive hands-on experience managing and troubleshooting production AWS environments.
• Strong Python and FastAPI development experience.
• Demonstrated expertise with AWS ECS, Fargate, IAM, VPC networking, ALB, CloudWatch, Cognito and S3.
• Experience assessing cloud infrastructure security and remediating vulnerabilities.
• Proven experience with application scalability, load testing and production performance optimization.
• Strong SQL and PostgreSQL experience.
• Experience with Docker, CI/CD, GitHub Actions and infrastructure as code.
• Ability to independently review an existing technical architecture and implement improvements.

Highly preferred qualifications

• AWS Certified Solutions Architect – Professional, or equivalent demonstrated expertise.
• AWS Certified DevOps Engineer – Professional.
• AWS Certified Security – Specialty.
• Experience with AWS CloudFormation.
• Experience with Snowflake, Prefect and asynchronous/background processing.
• Experience with AI-powered applications and third-party LLM APIs.
• Experience designing secure, multi-tenant SaaS applications.
• Experience with security assessments, penetration-test remediation and production launch readiness.

Ideal freelancer profile
We need a senior engineer who combines the skills of an AWS cloud infrastructure specialist with those of a hands-on Python backend developer.
The ideal candidate has previously taken an application from early development into secure, scalable production use and is comfortable working with a small team of AI developers and data scientists.