I'm Samuel Fajreldines

I am a specialist in the entire JavaScript and TypeScript ecosystem (including Node.js, React, Angular and Vue.js)

I am expert in AI and in creating AI integrated solutions

I am expert in DevOps and Serverless Architecture (AWS, Google Cloud and Azure)

I am expert in PHP and its frameworks (such as Codeigniter and Laravel).

Samuel Fajreldines

I am a specialist in the entire JavaScript and TypeScript ecosystem.

I am expert in AI and in creating AI integrated solutions.

I am expert in DevOps and Serverless Architecture

I am expert in PHP and its frameworks.

+55 (51) 99226-5039 samuelfajreldines@gmail.com

Latest Blog Posts

Creating a Native Knowledge Graph System with MongoDB, S3 and LangChain

Creating a Native Knowledge Graph System with MongoDB, S3 and LangChain

por Samuel Fajreldines | 21/07/2025 00:52 | Artificial Intelligence

Executive Summary We built a comprehensive Knowledge Graph System from scratch using modern web technologies to power AI-driven health and fitness applications. This native implementation leverages MongoDB for episode storage, Amazon S3 for vector persistence, OpenAI embeddings for semantic search, and LangChain for AI tool integration, creating a scalable, cost-effective, and privacy-focused solution for managing complex health data relationships. What is a Knowledge Graph a...

Internationalizing React Apps and Backend Services: Best Practices for i18n

Internationalizing React Apps and Backend Services: Best Practices for i18n

por Samuel Fajreldines | 21/07/2025 00:52 |

Reaching a global audience requires building applications that can handle multiple languages and cultural nuances effectively. Internationalization (i18n) is a crucial part of modern software projects, as it turns region-specific code into flexible systems that adapt to each user’s locale. When implemented properly, i18n significantly enhances user experience and opens the door to broader market opportunities. To support i18n in both React on the frontend and in backend servi...

Building a Fitness AI Agent with LangChain.js: A Real-World Implementation

Building a Fitness AI Agent with LangChain.js: A Real-World Implementation

por Samuel Fajreldines | 19/07/2025 09:00 | AI Development

Building intelligent AI agents that can understand natural language and perform complex tasks has become increasingly important in modern app development. Recently, I built a comprehensive fitness AI agent for my app using LangChain.js that can understand user input, make intelligent decisions, and execute appropriate actions. This post explores the real implementation, architecture decisions, and lessons learned. The Challenge: Building a Contextual Fitness Agent The fitness...

Mastering Langchainjs to Coordinate Tool and Function Calls Using AI Agents

Mastering Langchainjs to Coordinate Tool and Function Calls Using AI Agents

por Samuel Fajreldines | 17/07/2025 22:34 |

AI-driven development is increasingly reshaping how software solutions are built and delivered. As natural language processing (NLP) models continue to grow in sophistication, developers need powerful new frameworks to integrate these models effectively. Langchainjs stands out in this space by offering a set of utilities to coordinate tool usage and function calling, employing a chain-of-thought mechanism to provide coherent, step-by-step decision-making. This article dives i...

Long-Term Memory for AI: How Graphiti Works for Building Real Smart Applications

Long-Term Memory for AI: How Graphiti Works for Building Real Smart Applications

por Samuel Fajreldines | 14/07/2025 19:27 | AI & Machine Learning

Graphiti transforms ever-changing data into a bi-temporal knowledge graph that your AI agents can query in milliseconds. In this guide you'll learn why it exists, how it works, and how to build a Personal Financial AI Coach that learns from your daily spending habits and provides personalized advice to help you make better money decisions. 1 What is Graphiti? Graphiti is an open-source Python framework for building real-time, bi-temporal knowledge graphs tailored to retri...

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My Resume

Experience

  • SecurityScoreCard

    Nov. 2023 - Present

    New York, United States

    Senior Software Engineer

    I joined SecurityScorecard, a leading organization with over 400 employees, as a Senior Software Engineer, focusing primarily on frontend development. My role involves designing and building user-centric interfaces, optimizing performance, and ensuring seamless user experiences across our web applications.

    I specialize in modern frontend technologies, crafting scalable and maintainable codebases while integrating them efficiently with backend systems. I also contribute to UI/UX improvements, enhancing usability and accessibility to align with industry best practices.

    Beyond development, I collaborate closely with designers, product managers, and backend engineers to ensure cohesive and intuitive applications. By leveraging my expertise in frontend architecture and performance optimization, I help SecurityScorecard deliver high-quality cybersecurity insights through fast, responsive, and visually compelling interfaces.

    Highlights:

    Reduced system bundle size by 90%, leading to an 8x improvement in load speed.

    Eliminated system duplicate requests, improving backend efficiency and reducing server load.

    Technologies Used:

    Node.js Terraform React Redux / React Query Typescript AWS Playwright Cypress

  • Mahisoft Inc

    Dec. 2022 - Nov. 2023

    New York, United States

    Senior Software Engineer

    I joined Mahisoft as a Senior Software Engineer, where I serve as the lead technologist responsible for all the technology and systems related to the projects under my charge.

    I specialize in translating the directives from the board members of Top Trader League into functional, scalable code. My work often involves architecting backend systems, optimizing database queries, and building responsive, user-friendly front-end interfaces to convert the leadership team's vision into tangible results that drive business impact.

    One of my key responsibilities is writing efficient and maintainable code that not only meets but exceeds the technical requirements, ensuring that our software solutions are robust and scalable.

    Highlights:

    Implemented an asynchronous messaging system, reducing database overuse and improving efficiency.

    Implemented serverless architecture using Google Cloud, enabling a highly scalable and cost-efficient infrastructure.

    Technologies Used:

    Node.js PHP (Laravel) React Redux / React Query Google Cloud AWS Terraform

  • Vagalume Midia

    Aug. 2021 - Dec. 2022

    Senior Software Engineer

    I was privileged to join Vagalume as a Senior Full Stack Developer, brought on board by the company's owner, Daniel. At Vagalume, I was the go-to person for a wide array of tasks spanning both coding and DevOps.

    As the largest enterprise I've worked for in terms of user base and visitor traffic, Vagalume provided a complex and stimulating environment where I honed my skills in DevOps and high-scalability systems. The guidance and mentorship from Daniel have been invaluable, shaping not only my professional development but also forging a lasting friendship.

    One of my most notable contributions was the complete overhaul of Vagalume's radio systems. This involved rearchitecting the infrastructure and rewriting the codebase. The end result was a significant boost in system performance and a marked reduction in AWS operating costs.

    Highlights:

    Learned DevOps under Daniel, one of the world's top AWS experts, gaining deep expertise in cloud infrastructure.

    Refactored Vagalume Radios in Node.js from scratch, enhancing efficiency, scalability, and reducing costs.

    Technologies Used:

    Node.js PHP React Redux / React Query Vue.js AWS Terraform

  • Anilha

    Feb. 2019 - Dec. 2021

    Side period

    Founder

    I believe that the best way to learn is by doing something with what you are learning.

    So, during my free time, I started an app called Anilha. Anilha means dumbbell in Portuguese and the app was designed to help users with flexible diet and workouts.

    I can say with 100% certainty that Anilha was the biggest factor in my learning process.

    Technologies Used:

    Node.js Ionic Angular AWS Lambda DynamoDB Terraform

  • Secretária Virtual

    Sep. 2019 - Aug. 2021

    Senior Software Engineer

    I had the privilege of being recruited by Leonardo Leffa, a close friend and mentor, to oversee the technology initiatives across a diverse portfolio of enterprises under the umbrella of Secretaria Virtual. In this capacity, my responsibilities extended beyond mere code writing to shaping the development processes and workflows that governed how tasks were requested by users and collaborators within the company.

    During my tenure at Secretaria Virtual, I led an array of complex development projects as directed by the company's senior leadership. My scope of work covered:

    Infrastructure Development: Ensuring robust, scalable backend solutions.

    System Development: Architecting and coding business-critical applications.

    Monitoring & Testing: Establishing metrics and frameworks to ensure software reliability.

    I was instrumental in ushering the company into a new technological era by advocating for and implementing cloud computing solutions and continuous integration practices. Moreover, I led the shift towards Agile development by introducing the Scrum methodology, fostering a more collaborative and efficient work environment.

    Technologies Used:

    Node.js PHP AngularJS Laravel CodeIgniter Ionic

  • E-TRUST

    Sep. 2017 - Sep. 2019

    Senior Software Engineer

    Operating in the critical sphere of Information Security, E-trust necessitates the utmost safeguarding of data across all its platforms.

    As a Senior Developer at E-trust, I was entrusted with a multi-faceted role that included not only coding but also shaping the development processes in collaboration with upper management. My primary mission was to innovate new features while modernizing both frontend and backend architectures of our Horacius system—all while maintaining rigorous security protocols.

    In pursuit of code excellence and efficient workflows, I established clean coding practices based on Object-Oriented Programming (OOP) principles. I was also instrumental in introducing continuous integration processes, which included automated migrations and code validation through specialized robotic checks.

    Among my proudest achievements was the complete revamping of the Horacius system's frontend. The challenge was not just to modernize it but also to ensure backward compatibility with legacy systems. The successful implementation resonated well with our client base, which includes some of Brazil's largest banks and corporations.

    Being at the forefront of creating the company's code culture, I was exposed to substantial responsibilities and unparalleled learning experiences, particularly in the realms of security and DevOps.

    Technologies Used:

    PHP Microsoft SQL Server Windows Server

Education

  • UniRitter

    2015 - 2018

    UniRitter Laureate International Universities

    Bachelor of Computer Science

    Engaged in a rigorous program at UniRitter Laureate International Universities, renowned as one of the top institutions in the country. Excelled in System Analysis and Development, receiving accolades for academic excellence. Although I did not complete the degree due to career opportunities in the field, my foundational education and achievements at UniRitter have significantly contributed to my professional capabilities and expertise.

Featured Blog Posts

  • Long-Term Memory for AI: How Graphiti Works for Building Real Smart Applications

    Graphiti transforms ever-changing data into a bi-temporal knowledge graph that your AI agents can query in milliseconds. In this guide you'll learn why it exists, how it works, and how to build a Personal Financial AI Coach that learns from your daily spending habits and provides personalized advice to help you make better money decisions. 1 What is Graphiti? Graphiti is an open-source Python framework for building real-time, bi-temporal knowledge graphs tailored to retri...

    https://www.samuelfaj.com/posts/2025-07-14-222718/index.html

  • Mastering Multi-Cloud with Terraform: Deploying Infrastructure on Google Cloud and AWS

    The proliferation of cloud platforms has ushered in a new era of flexibility and opportunity for software professionals and organizations. While choosing a single provider can streamline certain operations, leveraging multiple clouds has become increasingly attractive for achieving redundancy, optimizing costs, and accessing the unique offerings of each provider. This is where Infrastructure as Code (IaC) tools like Terraform come into play. By using Terraform to deploy to bo...

    https://www.samuelfaj.com/posts/2025-01-24-115800/index.html

  • Mastering Transactions in Modern Software Engineering

    Transactions lie at the heart of any robust application that deals with sensitive or critical data updates. Whether you're developing a high-traffic e-commerce platform, a financial services dashboard, or a social media application, the integrity of your data hinges on well-established transaction mechanisms. In modern Software Engineering, the term "transactions" extends beyond simple database commits and rollbacks. It includes distributed transactions, sophisticated concurr...

    https://www.samuelfaj.com/posts/2025-02-11-141552/index.html

  • The Ultimate Guide to Using React Query: Why and How to Implement It

    Introduction In the modern web development landscape, efficient data fetching and state management are crucial for building responsive and user-friendly applications. React Query, often described as "the missing data-fetching library for React," simplifies these aspects by providing powerful hooks for fetching, caching, and updating asynchronous data in React applications. In this comprehensive guide, we'll explore why React Query has become an indispensable tool fo...

    https://www.samuelfaj.com/posts/2024-10-22-182435/index.html

  • Implementing Event-Driven Architecture with AWS and Node.js

    Modern applications demand scalability, flexibility, and real-time responsiveness. To meet these requirements, developers are increasingly turning to event-driven architecture (EDA), a paradigm that decouples components and enables systems to react to events as they occur. In this post, we'll explore how to implement an event-driven architecture using AWS and Node.js, unlocking the full potential of cloud-native applications. Understanding Event-Driven Architecture At its cor...

    https://www.samuelfaj.com/posts/2025-01-20-163757/index.html

  • All the Types of Tests in Software Development

    Software testing is essential for delivering reliable, scalable, and secure applications. By rigorously testing every part of an application, teams catch bugs earlier, reduce technical debt, and achieve higher quality standards. Below is a detailed overview of the most common types of tests in software development, along with practical examples using JavaScript and Node.js. This guide demonstrates how multiple levels of testing can be integrated into a comprehensive testing s...

    https://www.samuelfaj.com/posts/2025-02-25-010444/index.html