Senior Python Backend Engineer at Happio Ltd | Jobyssey

About Us
We’re building a mental wellness app designed to deliver personalised, accessible, and impactful support to users worldwide. Our mobile app is already live and growing fast, and we’re now looking for a talented Backend Developer to join our team and help take the product to the next level.

The Role
You'll own and evolve the server-side logic that powers our apps — designing and shipping APIs consumed by mobile and web clients, strengthening our microservices ecosystem, and helping us scale reliably and securely. You'll work closely with frontend and mobile engineers, DevOps, and product.

Key Responsibilities
API & Auth

Design and maintain RESTful APIs for iOS, Android, and web
Build high-throughput async endpoints
Implement JWT auth flows and OAuth 2.0 social login (Apple, Google)
Microservices & Architecture

Develop and maintain core services: User, Content, Tracking, Analytics, Notification
Design stateless, fault-tolerant services for horizontal scaling
Contribute to Golang services for high-concurrency analytics and notification dispatch
Database & Caching

Write optimized PostgreSQL queries; design schema migrations indexes
Implement time-based table partitioning for analytics and journal data
Configure PgBouncer pooling, read/write splitting, and materialized views
Build and invalidate multi-layer Redis caches (sessions, content metadata, preferences)
Integrations

Apple HealthKit (sleep, HRV, mindful minutes, activity sync)
In-app purchases: App Store API and Google Play Billing verification
Push notifications via Firebase Cloud Messaging (iOS & Android)
Stripe for web subscription payments; Amazon Polly for TTS in meditations
Security & GDPR

GDPR features: data export (JSON), 30-day automated deletion, consent management
AES-256-GCM encryption for sensitive mental health data fields
Enforce TLS 1.3, HSTS, Perfect Forward Secrecy; contribute to RBAC and audit logging
DevOps & Quality

Maintain Dockerfiles and multi-stage build configs; participate in GitLab CI/CD pipeline
Support blue-green deployments and canary rollouts (10% traffic routing)
Write unit, integration, and contract tests using pytest

Requirements
Must Have

5+ years backend development in Python
Confident working with the Flask and FastAPI frameworks.
Experience with Golang, JavaScript, and HTML.
VPS management skills on AWS: initial setup, application deployment, performance optimization, updates, security, and monitoring.
Experience working with Elasticsearch.
Strong PostgreSQL skills: schema design, query optimization, indexing, migrations
Redis for caching, session management, and rate limiting
JWT authentication, OAuth 2.0, and security best practices
Experience with pytest and contributing to CI/CD pipelines
Comfortable working in a Docker-based microservices environment
Knowledge of GDPR requirements and privacy-by-design practices
Proficiency with Git and collaborative workflows (GitFlow)

AI & Automation

Strong understanding of AI-powered development workflows and modern AI tools
Experience using AI-assisted coding tools such as ChatGPT, Claude, GitHub Copilot, Cursor, and Lovable
Ability to leverage AI tools to improve development speed, debugging, documentation, testing, and code quality
Understanding of AI integrations, LLM APIs, prompt engineering, and AI-assisted automation workflows
Experience working with AI-generated code while maintaining high standards for security, scalability, and maintainability

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