
Mauricio Klein
Verified Expert in Engineering
Full-stack Developer
Valencia, Spain
Toptal member since September 9, 2022
Mauricio is a highly experienced full-stack engineer with over 10 years of expertise in various aspects of software development, including front end, back end, infrastructure, and DevOps. He holds three AWS certifications and is well-versed in AWS workloads, serverless architecture, React, and event-driven applications. Mauricio has a strong track record of enhancing MVPs and guaranteeing the seamless operation of highly intricate applications, with a commitment to excellence.
Portfolio
Experience
- Amazon Web Services (AWS) - 6 years
- TypeScript - 5 years
- Serverless Architecture - 5 years
- React - 5 years
- Leadership - 3 years
- Python - 3 years
- Beautiful Soup - 2 years
- Flask - 1 year
Preferred Environment
MacOS, Slack, Postman, Visual Studio Code (VS Code), Docker, Notion, Make (formerly Integromat), n8n
The most amazing...
...project I've participated in was leading the development of the front-end portion for the support environments on Amazon CodeCatalyst.
Work Experience
Full-stack Engineer
Wish Pool LLC.
- Created a social media network for a specific purpose (under NDA).
- Implemented a full-stack application using Next.js as well as ShadCN as a component library.
- Set up the whole infrastructure, including Heroku, Supabase, Clerk, and Elasticsearch, among others.
Staff Software Engineer
Rithum
- Worked on the adoption of Notion as the company's central knowledge system. The process required deep knowledge about Notion itself, integrations, massive data migration, and automation.
- Proposed and implemented a CLI application (Python), automating multiple manual processes the team performs daily. Measure after three sprints showed that the time spent by the team in these routines was reduced by over 70%.
- Handled a project to migrate over 1000 pages from Confluence to Notion as part of the company's plans to decommission Confluence. Work required workspace configuration, automation, and integrations via Notion API.
- Performed as tech lead of 10+ engineers, spread across three different timezones. Responsible for architectural decisions, technical support to the team, and coordination with stakeholders regarding goals, deliveries, and quarterly plans.
- Worked actively in the implementation of a serverless event-driven system in NodeJS/Typescript that runs on AWS. The application was responsible for suggesting cheaper and faster ways to ship goods to clients while respecting delivery constraints.
- Authored 10's Make.com scenarios to automate various initiatives, from report generation to data migration from Confluence and Google Drive to Notion.
- Worked on Python applications to automatically collect, process and present data used for report generation. Data was consumed from multiple sources (S3, Redshift, Postgres, etc.), processed using Pandas and NumPy, and exposed internally using Flask.
- Created 10's of Airflow DAGs, responsible for critical workflows in the team. DAGs relied on datasets for triggers and leveraged Python scripts to perform different calculations and process data based on each scenario.
Back-end Node.js Developer
Trantor
- Developed and maintained back-end applications in Node.js using TypeScript.
- Developed front-end applications in React using TypeScript.
- Developed a middleware application for communication with Windows API in Rust.
- Worked on project improvements that are now in the building and testing phase, using the incremental building with Turborepo, Docker, and GitHub Actions as CI/CD.
Serverless Specialist
SUBSCRIBE PRO INC
- Developed a testing environment, allowing the team to test the application end-to-end locally without depending on the cloud.
- Used LocalStack and many AWS services (e.g., S3, API Gateway, ELB, Lambdas, etc.) heavily.
- Added support to Docker on existing applications, allowing them to run as containers in a more fine-grained way.
Software Development Engineer
Amazon Web Services (AWS)
- Led the front-end development of development environments to support Amazon CodeCatalyst. The application consists of a React/TypeScript application globally distributed, covered with unit tests using RTL and E2E tests using Puppeteer.
- Proposed and implemented Amazon DynamoDB modeling, improving extensibility and maintainability. This modeling extended the data storage capabilities to new business requirements with minimum effort.
- Supported a sister team in the implementation of their infrastructure using AWS CDK. The application consisted of serverless architecture and a high-request volume AWS Fargate cluster served by a load balancer and Amazon API Gateway.
- Conducted more than 30 technical interviews via phone, screen, and onsite.
- Presented technical architectures for internal audiences with over 50 participants.
- Implemented 10's Python scripts for different purposes, including maintenance and adjustments in AWS resources using Boto3, ETL using pandas and NumPy, and internal microservices implemented using Flask for interservice operation.
- Worked on the design and implementation of serverless apps running in AWS. Applications were written in Node.js/TypeScript, running in Lambda/ECS clusters (using Docker), and exposed internally via API Gateway. DynamoDB was used as internal storage.
Lead Back-end Engineer
Blacklane
- Acted as tech lead of a team of 8+ engineers across two time zones, integrating external partners and airlines. Responsibilities included architectural decisions, training, mentoring, and implementing microservices in Python and Ruby.
- Led the integration of a big airline, which increased the company's revenue by around 20%. The project was ambitious with a very short deadline, which required ownership, a divide-and-conquer approach, and strong leadership from my side.
- Proposed and created a toolbox CLI in Python, helping engineers across the department to easily migrate their apps into Kubernetes, generating all the K8s artifacts for the application. This CLI was decisive for the adoption of K8s in the department.
- Maintained the AWS infrastructure of the whole company as a DevOps engineer. Supported services included Amazon RDS (MySQL), Amazon EC2 Fleet, Amazon Route 53, EKS, and AWS Lambda.
- Acted as an AWS internal reference, supporting other teams in making the best use of the cloud and, whenever necessary, working alongside the team to prepare their cloud environment.
- Supported the mobile team in implementing back- to front-end architecture in Kotlin, fastening the team's delivery process.
- Directed the assessment of Datadog as a monitoring solution and the internal beta program for its implementation.
Senior Software Engineer
fromAtoB
- Led a team of three back-end engineers responsible for the integration of providers into the platform, performing technical analysis, collecting business requirements, and managing the team's backlog.
- Introduced the integration process via web scrapping as an alternative for bus providers without a direct API connection. Web scraping was implemented using Python and Beautiful Soup, exposing the results and booking process via a Flask application.
- Participated in the implementation of the new search system using Go and goroutines to fan out search requests. This new system reduced the number of Kubernetes pods necessary to handle the company load.
- Supported the front-end team with the Vue app, extending the support to additional providers due to limited bandwidth. Later, part of the front-end workload was delegated to my team, which became responsible for integrating the micro front end.
- Performed ethical reverse engineering to craft custom integrations for partners with no public API exposed. Reverse engineering was performed following a black box model, and connectors were implemented in Python and exposed via a Flask API.
Software Engineer
Jura Online
- Led the company's website migration from a Scala monolith to a React application with a new company identity and server-side rendering.
- Migrated a monolith API written in Java and Scala to a microservice architecture using Ruby.
- Improved the E2E testability of all services by adding Docker support to individual services and Docker Compose for the orchestration. This improved the delivery confidence across the engineering department.
- Worked in a 5-hours time zone difference from the company's main office. Demonstrated extensive use of written communication and decision-making to keep all parts aligned and track progress and deadlines.
Software Developer
Codeminer42
- Worked as a contractor for PagSeguro, Brazil's biggest digital payment service company, at that time.
- Handled the backporting of production features to a sandbox environment, allowing technical customers to test the latest features before pushing them to production.
- Wrote application in Java with Enterprise Java Bean (EJB) and Java Message Service (JMS) and running on JBoss.
- Acted as a leader of the Codeminer's contractors on PagSeguro within a team of four engineers. Additionally to the technical work, I was the contact point with the customer, managing expectations and conflicts whenever necessary.
- Created Codeminer's engineering blog (blog.codeminer42.com) as one of the first authors. Today, the blog contains hundreds of posts and is popular among Brazil's Ruby/Rails community.
Software Developer
Zenvia
- Acted as a back-end engineer on Zenvia (NASDAQ: ZENV), one of Brazilian's leaders in the B2C digital market.
- Handled multiple initiatives in the Java space, from new features to software maintenance, in high-volume distributed applications running on top of Spring Framework and HAProxy.
- Worked on the Rails pilot project used to register and deliver customer content.
- Assisted in the adoption of Docker as a testing environment.
Software Performance Tester
Stefanini Group
- Worked as a contractor for Dell (NYSE: DELL), helping to load test their internal and customer-facing highly distributed web applications.
- Developed and executed test cases using HP LoadRunner, generating reports and conclusions based on these executions.
- Participated in go/no-go meetings, providing inputs from the test results and making data-driven decisions about the application's performance in production environments.
Software Developer
Netwall Tecnologia
- Developed a new application using C, C++, and SOAP protocols that monitored clients' servers (Windows and Unix), pushing server health metrics to the dashboard system. The application soon became the de facto metrics collection tool for the company.
- Built dozens of shell scripts used with the SOAP monitoring application to collect different server metrics, including memory, CPU, load, network, and processes.
- Worked on the main site's PHP application, fixing small bugs and performing layout adjustments.
- Attended technical meetings with customers, collecting their feedback and requirements and translating them into improvements in the application.
R&D Intern
HP Inc
- Worked as an intern in the Automatic Page Layout project, in conjunction with HP Labs in Palo Alto.
- Participated in regular meetings with HP Labs researchers to collect feedback about page content placement algorithm and plan the next iterations.
- Designed and developed algorithms for automated page layouts in the Java language.
- Created customer-facing prototypes in HTML and JavaScript using Swing for dynamic page rendering.
Experience
Emirates’ Complimentary Chauffeur-drive Service
I held regular meetings with the Emirates team to collect feedback and enhance the system, maximizing the chauffeur schedule and ensuring all Emirates customers had a car waiting for them at the airport gate.
After a successful initial beta program, Emirates awarded additional cities with Blacklane integration.
Jura Online Website
https://jura-online.de/I worked on migrating the Jura Online website and the back-end system.
The project was conducted on two fronts:
1. back-end migration
Migrated the monolith Java application into a microservice architecture powered by Ruby and Sinatra, collaborating with the company's CTO.
2. front-end migration
Migrated the front-end application with written templates in Scala, in a React application, using Redux as a store manager, and deployed on Amazon S3 served by Amazon CloudFront. I lead the front-end migration, managing two other engineers in the same project.
PagSeguro Sandbox
https://acesso.pagseguro.uol.com.br/sandboxMauricio worked on migrating functionalities of the "real" API into the Sandbox, allowing customers to test their integrations in a sane environment before making it available in production.
The project was implemented in Java with Enterprise Java Bean (EJB) and Java Message Service (JMS) and running on JBoss.
Co-founder of Jet5
The system was responsible for matching users requesting delivery of documents and small packages with motorcyclists willing to perform the job.
As a co-founder and lead back-end developer, my responsibility was to create the first PoC of the system. This PoC was built on Ruby on Rails, with Postgres as data storage. GeoLoc was part of the system, storing in the database the geolocation for pickup and dropoff of the package and calculating the price for the service.
Finally, push notifications were sent to drivers in the area nearby the pickup location, prospecting the jobs.
AI and Automation Consultant
Among the projects I can disclose, there was:
1. Migration of thousands of Confluence pages to Notion, which was achieved with a mix of a Make (former Integromat) scenario and Notion API requests to transform and migrate data.
2. Automating invoice generation, processing records in an Excel sheet, and generating invoices and notifications automatically for the concerned parts.
3. Multiple personal automation, from setting reminders to personal workflow automation, including integrations with Google Drive, ChatGPT, and external APIs, among others.
Node.js/Rust Developer for Enterprise Application
My duties included, but weren't limited to:
• Development and maintenance of back-end applications in Node.js (using TypeScript)
• Development of front-end applications in React (using TypeScript)
• Development of middleware application for communication with Windows API in Rust
• Existing project improvements in the building and testing phase, using the incremental building with Turborepo, Docker, and GitHub Actions as CI/CD
Tech stack: JavaScript, TypeScript, Node.js, Rust, React, Docker, GitHub Actions, Turborepo, PostgreSQL
Amazon CodeCatalyst
https://aws.amazon.com/codecatalyst/BACK-END DEVELOPMENT
• I developed a serverless application using Node.js, AWS Lambda, API Gateway, DynamoDB, and ECS. I optimized DynamoDB schemas to support evolving business needs, ensuring scalability and efficient data access.
FRONT-END DEVELOPMENT:
• I built the UI for the DevEnvironment feature from scratch using React, creating an intuitive interface tailored for developers.
INFRASTRUCTURE MANAGEMENT
• I managed infrastructure with AWS Cloud Development Kit (CDK) and AWS CloudFormation, automating deployments and maintaining scalable environments. I implemented monitoring and logging solutions with Amazon CloudWatch to ensure reliability.
COLLABORATION
• I assisted a sister team in creating their infrastructure using AWS CDK, which included Lambda, API Gateway, DynamoDB, ECS, and ELB services.
KEY ACHIEVEMENTS
• Developed the DevEnvironment UI from scratch.
• Led the infrastructure setup for a sister team using AWS CDK.
• Improved Amazon DynamoDB schema design for new business requirements.
Providers Integration via Web Scrapping
Q&A Social Platform
Education
Bachelor's Degree in Computer Engineering
Pontifícia Universidade Católica do Rio Grande do Sul - Porto Alegre, Brazil
Sandwich Exchange Course in Computer Engineering
University of Montpellier - Montpellier, France
Certifications
AWS Certified SysOps Administrator
Amazon Web Services
AWS Certified Developer
Amazon Web Services
AWS Certified Solutions Architect Associate
AWS
Skills
Libraries/APIs
React, Node.js, Beautiful Soup, Sidekiq, Vue, Java Message Service (JMS), OpenSSL, WMI, Ruby on Rails API, Google Maps SDK, Pandas, NumPy
Tools
AWS Cloud Development Kit (CDK), Notion, Notion API, Notion Formulas, Postman, Terraform, Apache, Jenkins, Apache Tomcat, LoadRunner, LaTeX, Adobe InDesign, Jekyll, GitHub Pages, Git, Subversion (SVN), AWS Step Functions, Amazon Simple Queue Service (SQS), AWS Fargate, Amazon EKS, Amazon CloudWatch, AWS ELB, AWS CodeCommit, AWS CodeBuild, AWS CodeDeploy, AWS CloudFormation, Amazon Elastic Container Registry (ECR), Amazon Elastic Container Service (ECS), GitHub, Docker Compose, NGINX, RabbitMQ, RSpec, n8n, Zapier, Make (formerly Integromat), Amazon CloudFront, Apache Airflow, Amazon CloudFront CDN, Shadcn
Languages
Go, JavaScript, Python, Ruby, TypeScript, Java, C, C++, Bash Script, PHP, Kotlin, Scala, Perl, HTML, CSS, Rust, GraphQL
Frameworks
Serverless Framework, Jest, Ruby on Rails (RoR), Next.js, Flask, NestJS, Redux, Spring, Swing, Sinatra, Hibernate, Apache Camel, Express.js, Tailwind CSS
Paradigms
Serverless Architecture, DevOps, Web Architecture, Automation
Platforms
Amazon Web Services (AWS), Docker, Linux, Kubernetes, Amazon EC2, Apache Kafka, JBoss, SharePoint, AWS Lambda, Google Cloud Platform (GCP), Windows, Unix, Heroku, LocalStack, Clerk
Storage
JSON, PostgreSQL, Amazon S3 (AWS S3), Amazon DynamoDB, Redis, MySQL, Datadog, GlusterFS, Elasticsearch
Other
APIs, Web Development, Full-stack, Make.com, Leadership, EJB3, WebLogic, HP SiteScope, SOAP, SMTP, Shell Scripting, Electronics, GitOps, Amazon API Gateway, Elastic Load Balancers, Amazon RDS, Amazon Route 53, AWS CodeArtifact, Technical Hiring, Code Review, Interviewing, React Hooks, Source Code Review, Presentations, Remote Work, Technical Writing, HAProxy, Programming, Web Scraping, ESLint, Turborepo, Reverse Engineering, Front-end, Back-end, Serverless, Web3, Supabase, Technical Leadership, Enterprise, Enterprise Systems, AWS NAT Gateway
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