Mauricio Klein, Developer in Valencia, Spain
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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.


Amazon Web Services (AWS), Node.js, TypeScript, Datadog, Notion, Notion API...
Amazon Web Services (AWS)
AWS Cloud Development Kit (CDK), React, Node.js, Serverless Architecture...
PostgreSQL, Sidekiq, Go, Git, Docker, Kubernetes, Apache Kafka, GitOps...




Preferred Environment

MacOS, Slack, Postman, Visual Studio Code (VS Code), Zsh, Docker, Notion, Notion API, Notion Formulas

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

Staff Software Engineer

2023 - PRESENT
  • Performed as a tech lead at cataLina EMEA team, responsible, among others, for rate shopping, a functionality part of the Delivery Suite product to enable participating suppliers to get the best shipping rate and help retailers cut shipping costs.
  • Proposed improvements in the release process, making it more automated and less error-prone, as a staff engineer. Also, led important initiatives in terms of resilience, testability, and best practices across the whole Delivery Suite.
  • Created Bulk Provisioning Tool, a CLI responsible for automating the process of onboarding and maintaining retailers in various Delivery Suite services (e.g., rate shopping, shipping labels, etc.).
  • Supported the team and product to trace the next quarter's goals and estimations.
  • Contributed to the full adoption of Notion in the company by running internal training, creating templates for different teams, supporting teams adopting Notion, and helping them maximize the tool.
  • Handled a project to migrate thousands of pages from Confluence to Notion as part of the company's plans to decommission Confluence. Work was based heavily on permissions settings, workspace configuration, automation, and integrations via Notion API.
Technologies: Amazon Web Services (AWS), Node.js, TypeScript, Datadog, Notion, Notion API, Notion Formulas

Software Development Engineer

2020 - 2023
Amazon Web Services (AWS)
  • Led the front-end development of development environments to support on Amazon CodeCatalyst. The application consists of a React 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 is still in use and was extended 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.
Technologies: AWS Cloud Development Kit (CDK), React, Node.js, Serverless Architecture, Docker, Git, TypeScript, Amazon DynamoDB, AWS Lambda, Amazon API Gateway, AWS Step Functions, Amazon Simple Queue Service (SQS), Amazon S3 (AWS S3), AWS Fargate, AWS ELB, AWS CodeCommit, AWS CodeBuild, AWS CodeDeploy, AWS CodeArtifact, Technical Hiring, Code Review, Interviewing, React Hooks, Source Code Review, AWS CloudFormation, Amazon Elastic Container Registry (ECR), Amazon Elastic Container Service (Amazon ECS), Presentations, Web Architecture, Jest, Express.js, JSON, Elastic Load Balancers, APIs, JavaScript, Web Development, Full-stack, Postman, Linux, Amazon Web Services (AWS), HTML

Lead Back-end Engineer

2018 - 2020
  • Acted as a tech lead, managing the integration of external partners and airlines and a distributed team of eight engineers across Europe.
  • Led the integration of a big airline, which increased the company's revenue by 20%. The project was ambitious with a short deadline, but I managed to coordinate the work among engineers in different time zones and deliver the full scope on time.
  • Incorporated a CLI tool automating the generation of Kubernetes manifest files, which increased the confidence and adoption of Kubernetes within the engineering 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.
  • Supported engineers on AWS and serverless architecture implementation and best practices.
  • 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.
Technologies: PostgreSQL, Sidekiq, Go, Git, Docker, Kubernetes, Apache Kafka, GitOps, Amazon EC2, Amazon S3 (AWS S3), AWS Fargate, AWS Lambda, Amazon EKS, Amazon CloudWatch, Amazon RDS, Amazon Route 53, AWS ELB, Redis, Node.js, Datadog, Kotlin, GitHub, Serverless Architecture, React, Jest, Web Scraping, Express.js, Python 3, JSON, Elastic Load Balancers, Serverless Framework, APIs, JavaScript, Web Development, Full-stack, Ruby on Rails (RoR), Postman, Ruby, AWS Cloud Development Kit (CDK), Linux, Amazon Web Services (AWS)

Senior Software Engineer

2017 - 2018
  • Led the team of three back-end engineers to integrate bus providers into the platform, performing technical leading, 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. This new integration process made it possible to onboard small providers and, thus, provide more options for our customers.
  • 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 application, extending the support to additional providers due to limited bandwidth.
  • Collected business requirements with new bus provider integration and translated them into the team's backlog.
Technologies: Go, Docker, Vue, Kubernetes, Git, TypeScript, Google Cloud Platform (GCP), Redis, PostgreSQL, Sidekiq, GitHub, Serverless Architecture, Node.js, Jest, Express.js, Python 3, JSON, Elastic Load Balancers, APIs, JavaScript, Web Development, Full-stack, Ruby on Rails (RoR), Postman, Serverless Framework, Linux

Software Engineer

2016 - 2017
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.
Technologies: Ruby, React, Redux, Git, TypeScript, Amazon EC2, AWS ELB, Amazon Route 53, Amazon S3 (AWS S3), Redis, MySQL, Sinatra, GitHub, Java, Scala, Remote Work, NGINX, Serverless Architecture, Node.js, Jest, Express.js, JSON, Elastic Load Balancers, APIs, JavaScript, Web Development, Full-stack, Ruby on Rails (RoR), Postman, PostgreSQL, Linux, Amazon Web Services (AWS), HTML, CSS, Docker Compose

Software Developer

2015 - 2016
  • 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 ( as one of the first authors. Today, the blog contains hundreds of posts and is popular among Brazil's Ruby/Rails community.
Technologies: Java, EJB3, JMS, JBoss, Apache, Git, MySQL, Docker, Docker Compose, Remote Work, Technical Writing, APIs, Web Development, Ruby on Rails (RoR), Ruby, Linux

Software Developer

2015 - 2015
  • 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.
Technologies: Java, Spring, Jenkins, Apache Tomcat, Git, PostgreSQL, GitHub, Hibernate, HAProxy, RabbitMQ, Apache Camel, APIs, Web Development, Ruby on Rails (RoR), Ruby, Linux

Software Performance Tester

2013 - 2015
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.
Technologies: LoadRunner, WebLogic, HP SiteScope, SharePoint, Subversion (SVN)

Software Developer

2010 - 2013
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.
Technologies: C, C++, SOAP, Linux, Bash Script, SMTP, PHP, Subversion (SVN), OpenSSL, WMI, Windows, Unix, Web Development

R&D Intern

2008 - 2010
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.
Technologies: Java, Swing, JavaScript, LaTeX, Shell Scripting, Adobe InDesign, Subversion (SVN), Perl, Unix, HTML

Emirates’ Complimentary Chauffeur-drive Service
I led the technical team that integrated Emirates with Blacklane and improved the system from an MVP design with manual steps to an automated product that collects information from flights and passengers provided by Emirates and schedules rides with Blacklane chauffeurs.

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
Jura Online is a German e-learning company that prepares law students for their final exams.
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
The sandbox environment for PagSeguro is part of Universo Online (UOL group), one of Brazilian's main digital payment services.

Mauricio 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

Jet5 was a small Brazilian startup focused on the delivery market by motorcycles.

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.

A social media profile focused on teaching Notion advanced concepts. The channel presents concepts and best practices about Notion beyond what's presented on other channels. It accepts audience requests for special content or questions.
2007 - 2014

Bachelor's Degree in Computer Engineering

Pontifícia Universidade Católica do Rio Grande do Sul - Porto Alegre, Brazil

2012 - 2013

Sandwich Exchange Course in Computer Engineering

University of Montpellier - Montpellier, France


AWS Certified SysOps Administrator

Amazon Web Services

APRIL 2020 - APRIL 2023

AWS Certified Developer

Amazon Web Services

APRIL 2019 - APRIL 2022

AWS Certified Solutions Architect Associate



React, Node.js, Sidekiq, Vue, JMS, OpenSSL, WMI, Ruby on Rails API, Google Maps SDK


AWS Cloud Development Kit (CDK), Notion, Notion API, Notion Formulas, Postman, 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 (Amazon ECS), GitHub, Docker Compose, NGINX, RabbitMQ, RSpec


Serverless Framework, Jest, Ruby on Rails (RoR), Redux, Spring, Swing, Sinatra, Hibernate, Apache Camel, Express.js


Go, JavaScript, Ruby, TypeScript, Java, C, C++, Bash Script, PHP, Kotlin, Scala, Perl, Python 3, HTML, CSS


Serverless Architecture, DevOps, Web Architecture


Amazon Web Services (AWS), Docker, Linux, Kubernetes, Amazon EC2, Apache Kafka, JBoss, SharePoint, AWS Lambda, Google Cloud Platform (GCP), Windows, Unix, Heroku


JSON, PostgreSQL, Amazon S3 (AWS S3), Amazon DynamoDB, Redis, MySQL, Datadog


APIs, Web Development, Full-stack, 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

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