Some ideas about writing code, since 2003

Celso Fernandes

Home | Github | Email | Location: Remote

After being in love with Linux since 1998, Ruby/Rails since 2010 and React/ES6 since 2016 you have some idea what you’ll find here.


2011-2012 Master Business Administration | Federal University of Itajubá

Graduation Work: Management Information System for Financial Analysis

2004-2009 BSc Computer Science | Federal University of Itajubá

Graduation Work: PaX and Arbitrary Code Execution

Working Experience

ClickFunnels 2019-Present (2 yrs 4 mos) Remote Position

Senior Software Consultant 1yr 3mos

Software Consultant 1yr 2mos

Trailblazer GmbH 2019-2020 (1 yr 2 mos) Remote Position

Senior Software Consultant

Agrosmart 2016-2019 (2 yrs 7 mos) Remote Position

Senior Software Engineer

Agrosmart is a digital agriculture platform that helps farmers make data-driven decisions. Focused on gathering data and deliver insights so farmers and suppliers.

At Agrosmart I was invited to handle the web product development, after being invested, there was a need to deliver the product as fast as possible, so my main goal was to roll features to customers, keeping stability and performance of the system.

We went from 0 to hundreds of customers, thousands of sensors sending data to the system and millions of data points generating agronomical insights to customers.

Zertico 2010-2016 (6 yrs 1 mo) - Itajubá/MG/Brazil


A startup with a focus on delivering premium Cloud Computing solutions to small and medium businesses. An IBM/SoftLayer partner.

Founded the company with my former boss Elias, from Foreclosure Listings, consolidating the infrastructure, focused on delivery high availability to customers.

We got some huge achievements, with some customers running at 99.999%, transferring petabytes of data per month in our network and managing about 400 Linux servers.

Agência Mestre 2008-2010 (1 yr 10 mos) - Itajubá/MG/Brazil

Project Manager

One of the biggest Brazilian digital marketing agencies with a focus on inbound marketing and SEO.

Agência Mestre is a spin-off of Foreclosure Listings, and I was invited to manage the product development of the company. My goal was to lead the development of SEO-Related products (website, backend engines, crawlers) and keep running the infrastructure.

The company released 3 products to monitor Google, Twitter and crawl the customer websites, delivering reports and tracking thousands of keywords and Twitter accounts.

Foreclosure Listings 2005-2008 (3 yrs 2 mo) - Itajubá/MG/Brazil

System Administrator

A US foreclosure website which offers thousands of new properties daily to home brokers.

My first professional experience, in a US company, very grateful for such a big first opportunity. My goal was to keep the company websites running, I was the first sysadmin to be hired, and managed the web servers (Apache), running PHP Application and accessing MySQL database.

I developed an HA strategy for the company, moving websites running on single bare metal servers to a cluster of machines, with replications increasing the uptime from (in some cases 99.5%) to more than 99.9% with low cost.

UNIFEI 2004-2005 (6 mos) - Itajubá/MG/Brazil


Internship on the Federal University of Itajubá during bachelor course.

I had an excellent opportunity to work with great professors. I was in charge to install and configure Linux on 2 laboratories that were used by university students.

I deployed the 2 laboratories (with about 35 machines each), with single authentication, stateful/shared (was non-cloud days) home directories.


I describe a little bit some technologies, my relationship with it and what I can do, alternatives are my second options to each one.

Ruby/Rails: After some years developing using PHP/Zend, when met Ruby/Rails in 2010 was love at first sight, and never looked back. I love the language philosophy, its productivity, semantics how it’s focused on developer happiness.

Alternatives: Node/Express, Crystal/Kemal/Lucky

I can develop full web systems, REST/GraphQL APIs, use design patterns, functional programming, have contributed to a lot of open source projects and use on a daily basis. I know the internals of the Rails framework, can optimize Ruby considering memory allocation, performance and uses in some other cases like CLI (Command Line).

ES6/React: To become a complete web developer, I focused 2016 and 2017 studying and improving JavaScript, the solution I felt more comfortable was using ES6/React/PropTypes. I also have delivered projects using React Native.

Alternatives: Preact, Vue, TypeScript

I can create a SPA (with redux, offline support), consuming a REST or GraphQL API, architect the application, test the behavior, do E2E testing and make performance tuning. I’m also comfortable using JSS/Styled Components.

PostgreSQL: I worked several years (2005-2010) with MySQL, Ruby community uses a lot of PostgreSQL and after using it, started to feel home, nowadays I feel comfortable using it for time series, geospatial, jsonb (specially for NoSQL usage), trees, full text. Also, the management is simple and robust.

Alternatives: MySQL

Can configure and manage for HA, backup and point-in-time recovery, analyze the performance of queries, and even the server performance, cache size, disk, and memory usage.

Puppet: Many years managing servers, use config management was a natural way, Puppet is simple, has a powerful DSL and has been the first mover for years, I use it from configuring my notebook, pet projects to production servers.

Alternatives: Chef

Use 3rd party and develop own modules, keep the auditable using it standalone or together with puppet server. Use Hiera (also encrypted) as ENC and develop some solutions on top of it.

C: I’m Bachelor in Computer Science, I never worked professionally with C, but as my first programming language, I have a deep love with it, love its simplicity, foundation and how it has been in use over decades.

Alternatives: Crystal, Node

I have fun with C


  • Portuguese: It’s my native language, have its phonetic/nasal sounds, much punctuation, but I love it :)
  • English: As a developer I’ve been reading tech and non-tech articles since 2000, conversation I started to develop in 2005 calling service providers, and writing is my weak point, but always practicing and improving while I write on my site. Nowadays I can keep a conversation for hours ;)
  • Spanish: As Brazilian, we are close to many Spanish-spoken countries, I like the language, I can understand (from Spain is harder for me), and maybe I can have some small talks
  • German: I also love this language, started studying on DW Deutsch, Warum Nicht? by myself, I can read some phrases, speaking is way hard to me, but trying to improve.


This is my personal space where I take notes about tech/programming things. Being in love with Linux since 1998, Ruby/Rails since 2010 and React/ES6 since 2016 you have some idea what you'll find here.

Celso Fernandes


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