Senior Back-End Engineer (Python & AWS)

I’m looking to hire a Senior Back-End Engineer to audit, document, and write comprehensive test cases for the back-end of my coaching application. The application is already live and has active users, so I’m looking for someone with strong experience working with production systems. You should be able to understand an existing codebase quickly, identify potential issues, document the architecture and workflows, and build reliable test coverage without disrupting the existing application. The back-end is primarily built with Python and AWS, so strong hands-on experience with Python back-end development and AWS is essential. What You’ll Do - Perform a comprehensive audit of the existing Python back-end. - Review the overall back-end architecture, application structure, APIs, services, authentication, authorization, middleware, validation, error handling, and security. - Review business logic and identify potential bugs, edge cases, technical debt, unnecessary complexity, duplication, and architectural problems. - Review database architecture, queries, relationships, indexes, transactions, and performance. - Review background jobs, queues, scheduled tasks, asynchronous workflows, and external integrations. - Identify potential scalability, reliability, security, and performance issues. - Provide practical recommendations for improving the existing system. AWS Architecture & Infrastructure A major part of this engagement will involve auditing the AWS infrastructure supporting the back-end. You should have strong hands-on experience with AWS services such as ECS, Fargate, EC2, Lambda, API Gateway, Application Load Balancer, CloudFront, Route 53, VPC, IAM, RDS, PostgreSQL, S3, SQS, SNS, ElastiCache, Redis, ECR, CloudWatch, Secrets Manager, and Parameter Store. You’ll review how the Python application is deployed, secured, connected, monitored, and scaled within AWS. The AWS audit should cover: - Infrastructure architecture - Networking and VPC configuration - IAM permissions and security groups - Application deployment - ECS/Fargate configuration - Load balancing - Database configuration - Caching - Queues - Logging and monitoring - Observability - Secrets management - Scalability and availability - Failure scenarios - Deployment processes - Rollback strategies - AWS cost optimization Testing & Test Cases A major responsibility will be establishing strong and meaningful test coverage for the existing back-end. You’ll write comprehensive unit tests, integration tests, and E2E/API tests for critical workflows. Testing should cover: - Authentication - Authorization - Validation - Error handling - Database interactions - Business logic - Edge cases - Failure scenarios - Background jobs - Queues - Asynchronous workflows, where applicable The goal is not simply to achieve a high code coverage percentage. We want meaningful tests around functionality that is critical to our users and business. Documentation You’ll document the existing back-end and AWS architecture, including: - Application structure - API architecture - Authentication and authorization flows - Database architecture - AWS infrastructure - AWS service dependencies - Data flows - Background jobs - External integrations - Deployment architecture - Environment configuration - Critical business workflows You should also document known technical debt, potential production risks, and recommended improvements. Architecture and data flow diagrams should be included where appropriate. Requirements - 5+ years of professional back-end engineering experience. - Strong production experience with Python and modern Python back-end frameworks. - Extensive hands-on experience with AWS and production AWS infrastructure. - Strong knowledge of ECS, Fargate, Lambda, RDS, S3, SQS, SNS, CloudWatch, IAM, VPC, ALB, ECR, ElastiCache, and related AWS services. - Strong experience with PostgreSQL and production databases. - Experience with Redis, queues, asynchronous processing, and distributed systems. - Strong understanding of authentication, authorization, application security, and AWS security. - Strong experience with automated testing, unit testing, integration testing, and E2E testing. Timeline & Budget This is a fixed-price task of $100, with an expected delivery timeline of 1 week from the start of the engagement.