Publication
WSGI: The Server-Application Interface for Python
https://www.toptal.com/developers/python/pythons-wsgi-server-application-interface
Leandro is available for hire
Hire LeandroLeandro Lima
Verified Expert in Engineering
Senior Full-stack Developer
São José dos Campos - State of São Paulo, Brazil
Toptal member since November 19, 2015
Bio
Leandro has over 20 years of experience with IT and has been working with Python since 2013. He has excellent analytical skills, combined with the know-how from combined years of experience and a degree in electrical engineering, and a passion for building efficient and cost-effective systems.
Portfolio
Aortii
TypeScript, Node.js, NestJS, React, React Router, Tailwind CSS...
LLS Software
TypeScript, React, React Router, Tailwind CSS, Node.js, Fastify, Knex.js...
Roundtable
Node.js, Python, Amazon Web Services (AWS), AWS Lambda, AWS IAM, Amazon EC2...
Experience
- Python - 12 years
- PostgreSQL - 10 years
- Amazon Web Services (AWS) - 10 years
- TypeScript - 8 years
- DevOps - 5 years
- Technical Leadership - 4 years
- Terraform - 1 year
- Node.js - 1 year
Preferred Environment
Linux, Amazon Web Services (AWS)
The most amazing...
...journey I've been on was turning the founders’ vision into a financial modeling SaaS—designing and developing the application and its cloud infrastructure.
Work Experience
Senior Full-stack Engineer
2026 - PRESENT
Aortii
- Built the MVP’s React front end from the ground up, translating Figma wireframes into a responsive, component-driven UI using Tailwind CSS and reusable layout/form components.
- Implemented core user onboarding and customer registration flows (client-side validation, error states, loading states, and navigation) using React Router and a clean page/feature structure.
- Developed the document management UI: upload experience, file listing, document type classification, and expiration metadata editing, aligning UX with security constraints for sensitive documents.
- Integrated the React app with a type-safe NestJS API, wiring end-to-end flows for document upload and metadata updates while improving UI feedback and styling through rapid iteration.
- Set up foundational AWS infrastructure for a secure credential/document-sharing MVP, including CloudFront and S3, and scoped IAM/GitHub OIDC role access for deployments.
- Deployed back-end services on an ECS cluster and integrated a PostgreSQL-compatible Aurora DSQL datastore plus S3 document storage with KMS encryption for security-first handling of sensitive files.
Technologies: TypeScript, Node.js, NestJS, React, React Router, Tailwind CSS, Amazon Web Services (AWS), Amazon CloudFront, Amazon S3 (AWS S3), AWS Key Management Service (KMS), AWS IAM, Amazon Elastic Container Service (ECS), Amazon Aurora DSQL, PostgreSQL, CI/CD Pipelines, GitHub Actions, REST APIs, Security, SaaS, Cloud Architecture, Minimum Viable Product (MVP), Database Design, Full-stack Development
Founder/Full-stack Engineer
2026 - 2026
LLS Software
- Designed and built a financial management system for Brazilian condominiums using TypeScript, React, and Fastify, leveraging Claude Code for AI-assisted development across the full stack, from database schema to UI components.
- Architected a TypeScript monorepo with shared ArkType validators and React Query key factories, ensuring end-to-end type safety between the Fastify REST API and the React front end with Tailwind CSS.
- Implemented identity-verified authentication by integrating with a government API for real-time citizen record validation, combined with JWT token rotation, Argon2 password hashing, and a four-axis role-based access control system.
- Developed a budget planning module with PostgreSQL-enforced constraints, GIST exclusion to prevent overlapping date ranges, trigger-based validation on monthly allocation arrays, and generated columns for automatic totals.
- Built a real-time multi-user synchronization layer using PostgreSQL NOTIFY/LISTEN and Server Sent Events, allowing all connected React clients to automatically see fresh data after any mutation, with support for horizontal scaling.
- Delivered a transaction tracking interface with multi-value splits across budget categories, monthly filtering, and spent-versus-planned visualization, wiring it to a Knex query layer with typed table definitions.
Technologies: TypeScript, React, React Router, Tailwind CSS, Node.js, Fastify, Knex.js, PostgreSQL, ArkType, JSON Web Tokens (JWT), Argon2, Server Sent Events (SSE), REST APIs, REST, Sentry, Claude Code, AI-assisted Development, Full-stack Development, SaaS, Database Design, Software Architecture, Security
Software and Infrastructure Engineer
2025 - 2026
Roundtable
- Designed and deployed a complete AWS infrastructure using Terraform, including CloudFront CDN architecture with multi-origin routing, VPC networking, CloudWatch monitoring, and ECS cluster.
- Built JWT-based Google Cloud authentication with AWS KMS signing, reducing the usage of long-lived authentication secrets and the surface for privilege escalation attacks.
- Implemented serverless data processing pipeline with Amazon Simple Queue Service (SQS), Node.js-based Lambda, including Valkey (Redis) cache, Amazon S3 storage, and cross-cloud replication.
- Refactored JavaScript codebase into a modular TypeScript monorepo with reusable components, including libraries to accelerate the development of future systems.
- Developed a complete Stripe metered billing integration, including incremental billing sync between Stripe and the database.
- Built a data extraction and conversion pipeline, structuring a large corpus of data in JSON format (millions of documents) from different sources into queryable data on PostgreSQL.
- Built an analytics data selection and fetching API using Node.js, AWS Lambda, API Gateway, and PostgreSQL, allowing researchers to easily select and extract data to use in experiments.
- Developed an internal React dashboard to support operations, integrating with the platform’s APIs to visualize key metrics and streamline internal processes.
Technologies: Node.js, Python, Amazon Web Services (AWS), AWS Lambda, AWS IAM, Amazon EC2, TypeScript, Terraform, Amazon Elastic Container Service (ECS), Amazon Aurora, PostgreSQL, Amazon ElastiCache, Amazon CloudFront, Amazon API Gateway, Amazon Simple Queue Service (SQS), Amazon S3 (AWS S3), Fastify, SQLAlchemy, Knex.js, Docker, CI/CD Pipelines, REST APIs, Serverless Architecture, API Integration, Full-stack, Infrastructure, Back-end, GitHub, Google Cloud Platform (GCP), SQL, JavaScript, Security, SaaS, AWS Cloud Security, Cloud Architecture, Software Architecture, Payment APIs, React, Stripe API, Database Design
Founder/Software and Infrastructure Engineer
2025 - 2025
Talk to Ellie
- Built a remote secretary service, integrating WhatsApp as a communication channel, Twilio as a number provider, Anthropic Claude as an AI model, and Stripe as a payment services provider.
- Developed an adaptation of the Model Context Protocol to run stateless as AWS Lambda functions, enabling the development of plugable functionality for the remote secretaries.
- Created a context management system, allowing the AI model powering the secretaries to remember previous conversations without polluting the context with unrelated data.
- Developed a double-sided contacts system, allowing secretaries working for different customers to efficiently handle conversations with different people with various authorization levels.
- Created a secure secrets storing mechanism, leveraging RDS and KMS, so that customers' API keys and passwords necessary to integrate with other systems were robustly stored with minimal attack surface.
- Developed a secure messaging storage architecture, leveraging KMS keys, preventing leaks of private conversations with the remote secretary even in face of a database compromise.
- Built mobile web interfaces with Angular accessible by dynamic short links, so users could complete tasks better suitable for a web interface as part of their interaction with the secretary.
- Built a Python monorepo architecture with private package interdependencies, allowing for minimal code to be shipped to AWS Lambda, reducing cold start times but maintaining efficient code sharing.
- Deployed application on AWS using Terraform and GitHub Actions.
Technologies: Python, AWS Lambda, Claude, Claude API, Amazon Bedrock, PostgreSQL, Twilio, Twilio API, WhatsApp Business, WhatsApp API, Amazon Simple Queue Service (SQS), Angular, Large Language Models (LLMs), Terraform, Stripe, Stripe API, Model Context Protocol (MCP), AWS Key Management Service (KMS), GitHub Actions, JavaScript, Security, SaaS, AWS Cloud Security, Cloud Architecture, Software Architecture, Payment APIs, Full-stack, Artificial Intelligence (AI), Database Design, Full-stack Development, Minimum Viable Product (MVP)
Software and Infrastructure Engineer
2025 - 2025
Fuse International
- Designed the base AWS infrastructure with VPC private and public subnets on Terraform.
- Migrated multiple PostgreSQL databases from Heroku and RDS to a single RDS instance, optimizing the cost-effectiveness of the infrastructure.
- Fine-tuned the PostgreSQL RDS instance to better handle aggregation queries on large datasets.
- Optimized PostgreSQL materialized view queries running on millions of rows to reduce execution time by about 50%.
- Developed a prototype for multiple-form data extraction and classification using Anthropic Claude.
- Kickstarted the creation of a document analysis application. Used Python FastAPI for application API, Celery for time-intensive background tasks, SQS for internal application messaging, S3 for large file storage, and PostgreSQL for relational data.
Technologies: Python, FastAPI, Amazon RDS, Amazon Web Services (AWS), GitHub Actions, Heroku, PostgreSQL, Amazon Bedrock, Anthropic, Claude, Terraform, Amazon Simple Queue Service (SQS), Celery, REST APIs, Mypy, Poetry, DevOps, Back-end Development, Startups, Optical Character Recognition (OCR), Full-stack, Infrastructure, AI Automation, Back-end, GitHub, SQL, JavaScript, SaaS, Software Architecture, Artificial Intelligence (AI), Full-stack Development, Minimum Viable Product (MVP)
Lead Software Engineer
2016 - 2025
ACG Business Analytics
- Helped the company owners over nearly a decade to design the software, break down and prioritize features, implement the system, build the infrastructure to run it, and assemble a team to sustain its development and operations.
- Built a sizeable financial modeling Python back end with a REST API as its primary interface, PostgreSQL as its primary storage, and performance optimizations in Rust and Cython.
- Used Angular 2+ to build the first interface for the API so that stakeholders could visualize its results, later evolving it into the first version of the product.
- Architected the AWS infrastructure to run the application as a SaaS. It started with a small EC2 instance and grew as needed to a scalable and highly available Kubernetes cluster with a managed RDS database for improved reliability.
- Developed a continuous deployment pipeline using GitHub Actions, using both GitHub amd64 workers and AWS CodeBuild arm64 workers. Used OIDC for secure integration into our AWS platform.
- Converted our originally hand-built infrastructure to IaC using Terraform to make its elements more maintainable, reusable, and accessible to other team members.
- Onboarded new members to the team, helping design their roles and guiding them on their familiarization with our architecture and professional development within the company.
- Served as a general technical advisor in software architecture and design, aiding in stakeholders' decision-making and guiding less senior developers on discussions and implementation details.
Technologies: Python, TypeScript, PostgreSQL, Rust, Bash, Amazon Web Services (AWS), Kubernetes, Amazon EKS, Amazon RDS, Amazon CloudFront, AWS ALB, AWS Lambda, Terraform, GitHub Actions, FastAPI, Amazon EC2, Amazon S3 (AWS S3), Amazon Route 53, SQLAlchemy, Flask, Technical Leadership, APIs, CI/CD Pipelines, Telegram Bots, REST APIs, Mypy, Poetry, Pytest, DevOps, Back-end Development, Scalable Application, Startups, API Integration, AWS CloudFormation, React, Model Context Protocol (MCP), Full-stack, Infrastructure, AI Automation, Back-end, GitHub, SQL, Data Analysis, JavaScript, Security, SaaS, AWS Cloud Security, Cloud Architecture, Software Architecture, Artificial Intelligence (AI), Database Design, Full-stack Development, Minimum Viable Product (MVP), Large Language Models (LLMs)
Software Developer
2016 - 2016
Manhan Group
- Implemented evolutionary strategies for a model using the Inspired Python library.
- Integrated with external evaluation software as optimization target of the evolutionary strategies.
- Created a command-line interface for the application based on customer requirements.
Technologies: Python, Inspyred, GitHub
Back-end Developer
2016 - 2016
Lactic Acid LLC
- Created an API to support car lease deal listings and search.
- Built an import mechanism to interface with a specialized web scraping service.
- Developed a mechanism to match scraped data with the vehicle database.
- Created a mechanism to keep data up to date with external sources.
- Wrote extensive documentation of code and API using Sphinx.
- Deployed a Debian GNU/Linux server with an application.
Technologies: PostgreSQL, SQLAlchemy, Flask, APIs, REST APIs, Back-end Development, Scalable Application, Startups, API Integration, Back-end, GitHub, SQL, Software Architecture, Full-stack, Full-stack Development, Minimum Viable Product (MVP)
Software Developer
2016 - 2016
Manhan Group
- Created a REST API as a web interface for a command-line application.
- Implemented data fetching from a PostgreSQL and PostGIS database.
- Built a command-line tool to import and update database data.
Technologies: PostgreSQL, Python, APIs, REST APIs, Flask, API Integration, Back-end, GitHub
Founder, CEO, and Development Engineer
2013 - 2015
DonePath Software e Monitoramento, Ltda.
- Developed a system to analyze real-time GPS tracker data and infer traffic and vehicle usage information.
- Built a system to allow parents to track their children's school transportation.
- Created a web app to help people encounter each other by broadcasting their geolocation to one another.
Technologies: Redis, PostgreSQL, SQLAlchemy, Python, REST APIs, Back-end Development, Scalable Application, Startups, Software Architecture, Full-stack Development
Development Engineer
2013 - 2014
Research Center for Inspection Technology/PUC-Rio
- Developed an algorithm to analyze and correct duct inspection data.
- Created software to automate embedded Linux installs.
- Built FPGA and CPLD control logic for several systems.
Technologies: FPGA, Bash, Python
Intern
2012 - 2012
Research Center for Inspection Technology/PUC-Rio
- Developed an FPGA implementation of Golay-24 error correcting code encoder and decoder for submarine telemetry data transfer.
- Wrote a software validator to test FPGA error correcting encoder.
- Programmed CPLD logic to control ultrasonic transducers.
Technologies: FPGA
Network and Systems Engineer
2003 - 2008
ViaLink
- Developed golden images for Linux servers providing network firewall, NAT, user access control, traffic shaping, HTTP, DNS, mail, and other services.
- Deployed and managed several Debian Linux servers, handling system updates, backups, and failovers, as well as managing security threats.
- Worked on network planning, establishing subclass allocation and routing paths for the company's CIDR pool according to availability and customer needs.
- Developed a new user access control system based on PPP over Ethernet, with Radius authentication on the MySQL database.
- Overhauled traffic shaping system, establishing a QoS model, using Netfilter to mark different packet streams and HTB to prioritize, shape, and policy traffic.
- Worked on troubleshooting, mitigating, and correcting network issues from the physical layer up to the logical layer, including malware propagation threats and malicious actors within the network.
- Collaborated with the backbone's counterpart on network configuration and troubleshooting.
Technologies: Debian Linux, Networking, Firewalls, NAT, IPv4, Ethernet, DNS, Infrastructure, Hosting, Security
Experience
Education
2006 - 2012
Bachelor's Degree in Electrical Engineering
Pontifical Catholic University of Rio de Janeiro - Rio de Janeiro, Brazil
Certifications
APRIL 2025 - APRIL 2028
AWS Certified Security – Specialty
Amazon Web Services Training and Certification
FEBRUARY 2025 - FEBRUARY 2028
AWS Certified Solutions Architect – Associate
Amazon Web Services Training and Certification
MAY 2014 - FEBRUARY 2022
Certified Scrum Product Owner
Scrum Alliance
Skills
Libraries/APIs
REST APIs, SQLAlchemy, Mypy, Node.js, React, Stripe API, Claude API, Twilio API, WhatsApp API, Stripe, React Router
Tools
Amazon EKS, Amazon CloudFront, Terraform, Pytest, GitHub, Amazon Simple Queue Service (SQS), Claude, Celery, AWS IAM, Amazon Elastic Container Service (ECS), Amazon ElastiCache, Knex.js, AWS CloudFormation, AWS Key Management Service (KMS), Sentry, Claude Code
Languages
Python, SQL, Bash, TypeScript, JavaScript, Rust
Paradigms
Database Design, Scrum, DevOps, Scalable Application, Serverless Architecture, Model Context Protocol (MCP), Hosting, Management, Agile Project Management, REST
Platforms
Amazon Web Services (AWS), AWS Lambda, Amazon EC2, Kubernetes, AWS ALB, Debian Linux, Linux, Heroku, Docker, Google Cloud Platform (GCP), Twilio
Storage
PostgreSQL, Amazon S3 (AWS S3), Redis, Amazon Aurora
Frameworks
Flask, Fastify, Angular, NestJS, Tailwind CSS, JSON Web Tokens (JWT)
Industry Expertise
Marketing, Project Management
Other
Back-end Development, Startups, API Integration, Back-end, Large Language Models (LLMs), SaaS, Cloud Architecture, Software Architecture, Minimum Viable Product (MVP), Full-stack Development, Amazon Route 53, Amazon RDS, GitHub Actions, FastAPI, Technical Leadership, APIs, CI/CD Pipelines, Telegram Bots, AWS Cloud Security, Full-stack, Infrastructure, AI Automation, Data Analysis, Security, Payment APIs, Artificial Intelligence (AI), FPGA, Networking, Firewalls, NAT, IPv4, Ethernet, DNS, Scrum Master, Scrum Product Owner, Amazon Bedrock, Anthropic, Poetry, Cloud Security, Data Security, Security Architecture, Security Management, Inspyred, Finance, Engineering, Aeronautics, Manufacturing, Amazon API Gateway, Optical Character Recognition (OCR), WhatsApp Business, Amazon Aurora DSQL, ArkType, Argon2, Server Sent Events (SSE), AI-assisted Development
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