Ennio is available for hire
Hire EnnioEnnio Alejandro Gonzalez Castillo
Verified Expert in Engineering
Back-end Developer
Valencia, Carabobo, Venezuela
Toptal member since August 4, 2021
Bio
Ennio is a back-end developer with over seven years of experience. He has worked with several technologies in his career, showing a complete set of skills while learning new languages/frameworks. His current stack of technologies is Node.js, NestJS, relational databases, Redis, and GraphQL. In his career, Ennio has gained experience in several industries, such as accounting, airport, blockchain, eCommerce, social networks, database, file management software, and healthcare.
Portfolio
Kimberly Clark Services, Inc. - Global IT
Express.js, Node.js, REST APIs, OpenAPI, API Gateways, Swagger, GraphQL, REST...
Capital Hill Management, Inc.
Node.js, Amazon Web Services (AWS), Microservices, Back-end, NestJS, MongoDB...
Kenility LLC
JavaScript, Node.js, Express.js, NestJS, Amazon Simple Queue Service (SQS)...
Experience
- SQL - 5 years
- Databases - 5 years
- PostgreSQL - 5 years
- REST APIs - 4 years
- TypeScript - 3 years
- NestJS - 3 years
- JavaScript - 3 years
- PHP - 2 years
Work Experience
API Engineer
2025 - 2026
Kimberly Clark Services, Inc. - Global IT
- Engineered and maintained scalable RESTful APIs within Kimberly-Clark’s multi-tiered enterprise architecture, facilitating seamless data flow and high availability for core business applications.
- Designed and optimized complex stored procedures and database queries using Microsoft SQL Server, enhancing data retrieval efficiency and reducing query execution times across production systems.
- Orchestrated cloud deployments and infrastructure configuration on Microsoft Azure, ensuring high-availability releases, minimal downtime, and smooth CI/CD deployment pipelines for enterprise projects.
- Spearheaded technical collaboration and API integration efforts across cross-functional engineering teams, establishing robust communication protocols and integration standards that accelerated feature delivery.
Technologies: Express.js, Node.js, REST APIs, OpenAPI, API Gateways, Swagger, GraphQL, REST, JavaScript, SQL, Jest, Test-driven Development (TDD), Microsoft SQL Server, Microsoft Teams, Azure
Back-end, Node.js, and NestJS Developer
2025 - 2025
Capital Hill Management, Inc.
- Developed four production-ready RESTful APIs—support plan, support plan subscriptions, cluster subscriptions, and subscription auth—using NestJS and MongoDB, fully aligned with client requirements and documented via Swagger for seamless integration.
- Implemented secure API authentication logic and integrated it into Swagger UI, enabling authenticated testing and significantly improving development and QA workflows.
- Built and deployed three automated cron jobs responsible for processing recurring subscription payments, ensuring reliable billing cycles, and reducing manual intervention by 100%.
Technologies: Node.js, Amazon Web Services (AWS), Microservices, Back-end, NestJS, MongoDB, Cloud Platforms, ECMAScript (ES6), E2E Testing, Auth, Swagger, Microsoft Teams, Cursor AI, Subscriptions, Payment APIs, APIs, API Integration, Git, GitHub, Back-end APIs, Back-end Development, Fastify, Cloud, RESTFul APIs, Postman, API Design, API Development
Back-end Developer
2022 - 2025
Kenility LLC
- Developed an integration with Google Business Profile to let users receive information about the apartments, houses, and units available via their chat on the business profile.
- Built an integration with Facebook Messenger to let users ask and receive information about the units available via Facebook Messenger.
- Analyzed and fixed bugs related to the real estate platform.
- Created a chatbot from scratch using a large language model (LLM) and custom-designed prompts to handle diverse customer interaction scenarios.
Technologies: JavaScript, Node.js, Express.js, NestJS, Amazon Simple Queue Service (SQS), Amazon Simple Notification Service (SNS), Google My Business API, Facebook API, Facebook Messenger API, RESTful Services, RESTful Development, Integration, API Integration, APIs, MongoDB, Webhooks, AI Prompts, ChatGPT Prompts, Large Language Models (LLMs), Heroku, OpenAI, OpenAI API, OpenAI GPT-3 API, OpenAI GPT-4 API, AI Tools, Vonage, Vonage SMS API, Vonage Voice API, Vonage Messages API, REST APIs, Back-end, Back-end APIs, Back-end Development, Git, GitHub, Cloud, Sockets, Socket.IO, WebSockets, AWS Command Line Interface (CLI), Active Server Pages (ASP), Third-party APIs, Artificial Intelligence (AI), ChatGPT API, ChatGPT, Customer Relationship Management (CRM), API Design, API Development, Facebook, Facebook SDK, API Gateways, Social Media APIs, Social Media, Social Media Platforms, AI Chatbots, Chatbots
TypeScript Back-end Engineer
2024 - 2024
Terminal Technologies Inc.
- Developed several API integrations, enabling Terminal’s platform to aggregate fleet data, including mileage, fuel consumption, and driver activity, for seamless client access with diverse telematics providers.
- Built integrations for multiple telematics APIs to retrieve real-time location data for fleet trucks, enabling centralized and accurate client tracking across diverse telematics systems.
- Streamlined documentation across multiple API integrations, improving clarity and consistency in both English and Spanish.
Technologies: TypeScript, JavaScript, AWS Lambda, Back-end Development, Amazon DynamoDB, Amazon Simple Queue Service (SQS), AWS Step Functions, Node.js, GitHub Actions, Reverse Engineering, Amazon Web Services (AWS), React, Watchdog, APIs, REST APIs, Back-end, Back-end APIs, Fastify, Datadog, Amazon CloudWatch, Git, GitHub, API Design, API Development
Team Lead
2019 - 2024
PynPon LLC
- Developed functional platform requirements guided by client data so that all the system specifications were agreed upon beforehand.
- Created the system architecture and selected the tech stack.
- Built the system database that met the client's needs, thanks to the functional requirements collected.
- Managed and assigned tasks to be done in the sprints for the back-end team.
- Deployed back-end and front-end projects on the servers every time new changes were uploaded.
- Managed the team regarding the implementation of Scrum in all the sprints carried out, which usually lasted two weeks each.
- Constructed the back-end architecture so the back end could communicate in real time with a mobile delivery app.
- Implemented a cache system to obtain products faster with Redis.
Technologies: Node.js, Scrum, Git, NestJS, SQL, PostgreSQL, Jira, Confluence, Bitbucket, Google Cloud Storage, Google Compute Engine (GCE), Scrum Master, Leadership, JavaScript, ECMAScript (ES6), TypeORM, Sockets, Docker, Linux, REST APIs, Google Cloud Platform (GCP), Google Cloud, NGINX, PM2, Auth0, Redis Cache, Redis, Team Management, Code Review, Source Code Review, Interviews, Interviewing, Technical Hiring, Visual Studio, Task Management, Task Analysis, Webhooks, APIs, Integration, API Integration, REST, RESTful Services, RESTful Development, Twilio, Twilio API, Datadog, Express.js, RESTFul APIs, GitHub, Bitbucket API, Stripe, Stripe API, Stripe Checkout, Socket.IO, WebSockets, Google APIs, Google Maps, Google Maps API, eCommerce, eCommerce APIs, Firebase, Redis Queue, API Development, API Gateways
TypeScript Back-end Developer
2023 - 2023
Stop Talking LLC
- Developed the integration with Stripe to fully satisfy the client's billing process needs.
- Designed and implemented the permissions system of the platform.
- Developed the integration with YouTube API to retrieve the users' channels and YouTube videos.
Technologies: TypeScript, Node.js, Stripe API, YouTube, YouTube API, YouTube Marketing, YouTube Ads, Next.js, Stripe Checkout, Stripe Connect API, Stripe Payments, Stripe Subscriptions, Stripe, Stripe Connect, Stripe Managed Accounts, SQL, PostgreSQL, Asana, Google Cloud, Google BigQuery, Vercel, Sentry, Vercel Analytics, Google APIs, Cloud, Back-end, Back-end APIs, Back-end Development, Databases, Database Architecture, API Development, Webhooks, API Gateways
Node.js Developer
2022 - 2022
Astrodon Corporation
- Developed an integration of Next.js with a Stripe API.
- Tracked customers' subscriptions with the possibility of canceling them at any point.
- Integrated the Stripe checkout and customer portal.
Technologies: Node.js, Stripe, API Integration, Stripe Payments, Stripe Checkout, Stripe Connect API, Stripe API, Stripe Subscriptions, Stripe Connect, Stripe Managed Accounts, Next.js, Payment APIs, Card Payments, Online Payments, Prisma, REST APIs, APIs, Integration, REST, RESTful Services, Webhooks, API Development
Back-end Developer
2022 - 2022
LeanXcale S.L.
- Developed a TypeORM driver/connector to be able to use TypeORM with the LeanXcale database engine.
- Tracked and reported bugs in the LeanXcale database engine.
- Debugged and fixed failing tests that TypeORM provides for every driver that it supports.
Technologies: JavaScript, TypeORM, ODBC, Docker, LeanXcale, SQL, TypeScript, Node.js, Apollo Server, Mocha, Git, GitLab, Back-end, Libraries, Databases, API Databases, Database Testing
Back-end Developer
2021 - 2022
Facerent Technologies Inc.
- Developed the integration between the back end and smart contracts to be able to mint NFTs.
- Created multiple end-to-end tests of the developed features.
- Generated a telegram bot that is used for moderation purposes.
- Built all the logic for in-app messaging, where users could send messages and share content.
- Added watermarks to all photos and videos uploaded to the platform.
- Generated thumbnails for every photo uploaded to the system.
- Developed the integration between the Stripe platform so that users could add coins to their wallets.
Technologies: JavaScript, Node.js, NestJS, Bots, GraphQL, Sockets, Redis, Redis Queue, Sharp, FFmpeg, Git, GitHub, Jira, Stripe, Polygon, Non-fungible Tokens (NFT), Docker, NGINX, Testing, Jest, Ethers.js, Integration, API Integration, RESTful Services, RESTful Development, APIs, Webhooks, Sentry, SendGrid, Back-end, Back-end APIs, Back-end Development, Databases, SQL, PostgreSQL, E2E Testing, Unit Testing, Apollo, Apollo Server, API Development, Social Media Login, Social Media
Developer
2021 - 2022
Ocho La Super App
- Researched the system's database to optimize and migrate it from MySQL to PostgreSQL.
- Gathered information to add new requirements to the implemented database.
- Created an API in NestJS to consume information from the new database.
Technologies: Node.js, NestJS, PostgreSQL, Jira, Confluence, Bitbucket, Algorithms, Databases, Database Architecture, JavaScript, ECMAScript (ES6), TypeORM, TypeScript, Passport.js, Windows, REST APIs, MySQL, Auth0, Twilio, API Development
Database Administrator
2018 - 2019
SkyFlot, C.A
- Managed the databases in all the different company systems.
- Optimized database queries which reduced the response times of the application.
- Synchronized the billing of 14 airports nationwide to make invoice reconciliation easier; this was a project that I worked on from scratch.
Technologies: PHP, MySQL, PostgreSQL, CodeIgniter, JavaScript, jQuery, Git, Software Architecture, GitLab, Leadership, REST APIs, Apache, HTML, CSS
Database Associate Professor
2016 - 2019
University of Carabobo
- Helped students in the practices related to the database class.
- Imparted knowledge associated with the creation of efficient database queries.
- Developed practical PostgreSQL workshops with the aim of evaluating students' knowledge in query creation.
Technologies: PostgreSQL, Linux, Java, Databases, Database Design, SQL Functions, SQL Triggers, University Teaching
Developer
2018 - 2018
Intelix Synergy, C.A
- Documented synchronization processes (stored in databases) between the company and the banking service provider. Previously it had stopped working and no one knew the reason.
- Fixed bugs discovered during the synchronization of bank movements.
- Optimized queries to databases; this area was an application bottleneck and was slowing down development.
Technologies: Java SE (Core Java), Transact-SQL (T-SQL), Subversion (SVN), SQL Triggers, SQL Functions, Documentation, API Development
Developer
2017 - 2017
Cardisoft F.P.
- Developed the modules for a telemedicine platform where patients and doctors communicated through video calls.
- Added new functionalities to an administrative system built with ASP.
- Created a user notification platform with a mass mailing feature.
Technologies: PHP, Active Server Pages (ASP), JavaScript, MySQL, HTML, CSS, API Development
Software Developer
2015 - 2016
Factory Soft
- Developed more than 1,500 accounting, payroll, and human resources reports.
- Optimized database queries to reduce response times.
- Generated OLAP cubes that consumed information from a database.
- Developed database triggers and functions to replicate products in real-time from a database. This was done for two database copies.
Technologies: JavaScript, .NET, ASPX, jQuery, Transact-SQL (T-SQL), Crystal Reports, OLAP, SQL Triggers, SQL Functions, HTML, CSS, SQL Server 2007, Microsoft SQL Server, API Development
Project History
LeanXcale TypeORM Driver
https://gitlab.com/leanxcale_public/typeorm/-/tree/leanXcaleA TypeORM driver for a new database engine. I was the developer in charge of creating the driver of LeanXcale for TypeORM so that this ORM could use the LeanXcale database engine at its core. With this implementation, users using LeanXcale can now use TypeORM to manage their connection with this engine.
NFT Social Media
An NFT social media app, where I was the back-end developer in charge of developing functionalities and features. The app lets users perform multiple actions, such as buying an NFT, minting an NFT, publishing posts, talking with each other, writing comments on posts, and more. I was also involved in the process of adding watermarks to the media files uploaded by users.
PynPon eCommerce
https://www.pynpon.com/For this eCommerce, I was in charge of raising the platform requirements and the subsequent build of a team of developers. Once the development team was made, I served as the project leader and database administrator. I was also in charge of reviewing the quality of the software generated by the back-end development team.
Invoice Synchronization
For an airport invoice synchronization project (carried out in PHP), I worked as the architect and developer and made use of a master-slave architecture, where the objective was to synchronize the invoices generated in 14 airports to a central office twice a day.
Telemedicine Platform
On a telemedicine platform, I worked as a full-stack developer and created the communication between client and server for making video calls between user and doctor. I also created a platform to generate medical recipes endorsed by doctors.
Education
2013 - 2019
Bachelor's Degree in Computer Science
University of Carabobo - Valencia, Carabobo, Venezuela
Certifications
JUNE 2021 - PRESENT
EF SET English Certificate 64/100 (C1 Advanced)
EF Standard English Test (EF SET)
MAY 2021 - PRESENT
JavaScript (Basic)
HackerRank
MAY 2021 - PRESENT
SQL (Basic)
HackerRank
MAY 2021 - PRESENT
SQL (Intermediate)
HackerRank
Skills
Libraries/APIs
REST APIs, Node.js, Passport.js, Sockets, jQuery, ASPX, Redis Queue, Sharp, FFmpeg, Stripe, ODBC, Stripe Connect API, Stripe API, Stripe Connect, Google My Business API, Facebook API, Facebook Messenger API, YouTube API, React, Auth, OpenAI API, Vonage SMS API, Vonage Voice API, Vonage Messages API, Twilio API, Back-end APIs, Socket.IO, Bitbucket API, Google APIs, Google Maps, Google Maps API, API Development, Facebook SDK, Social Media APIs, OpenAPI
Tools
Git, Slack, Bitbucket, Jira, Confluence, Google Compute Engine (GCE), GitLab, Crystal Reports, NGINX, PM2, Auth0, Cron, Subversion (SVN), Apache, GitHub, Mocha, Visual Studio, Stripe Checkout, Prisma, Amazon Simple Queue Service (SQS), Amazon Simple Notification Service (SNS), Asana, Sentry, AWS Step Functions, Microsoft Teams, AI Prompts, Watchdog, SendGrid, Postman, AWS Command Line Interface (CLI), Amazon CloudWatch, ChatGPT
Languages
SQL, TypeScript, Transact-SQL (T-SQL), JavaScript, PHP, ECMAScript (ES6), C++, C, Java SE (Core Java), Assembler, Prolog, Haskell, Java, Active Server Pages (ASP), HTML, CSS, GraphQL
Frameworks
NestJS, CodeIgniter, CodeIgniter 3, .NET, Jest, Next.js, Express.js, Swagger, Fastify
Paradigms
Database Design, Scrum, Business Intelligence (BI), OLAP, Testing, REST, RESTful Development, Microservices, E2E Testing, Unit Testing, Test-driven Development (TDD)
Storage
Databases, PostgreSQL, MySQL, Database Architecture, SQL Triggers, SQL Functions, Google Cloud Storage, Google Cloud, Redis Cache, Redis, LeanXcale, MongoDB, Amazon DynamoDB, SQL Server 2007, Microsoft SQL Server, Datadog, API Databases, Database Testing
Platforms
Windows, Linux, Google Cloud Platform (GCP), Docker, Amazon Web Services (AWS), YouTube, Vercel, AWS Lambda, Heroku, MacOS, Twilio, Firebase, Azure
Industry Expertise
Social Media
Other
Software, Algorithms, TypeORM, English, Leadership, Scrum Master, Software Architecture, Documentation, University Teaching, Servers, Networks, Bots, Polygon, Non-fungible Tokens (NFT), Apollo Server, Ethers.js, Team Management, Code Review, Source Code Review, Interviews, Interviewing, Technical Hiring, Task Management, Task Analysis, API Integration, Stripe Payments, Stripe Subscriptions, Stripe Managed Accounts, Payment APIs, Card Payments, Online Payments, APIs, Integration, RESTful Services, Webhooks, YouTube Marketing, YouTube Ads, Google BigQuery, Back-end Development, GitHub Actions, Reverse Engineering, Back-end, Cloud Platforms, Cursor AI, Subscriptions, ChatGPT Prompts, Large Language Models (LLMs), OpenAI, OpenAI GPT-3 API, OpenAI GPT-4 API, AI Tools, Vonage, Cloud, RESTFul APIs, WebSockets, Vercel Analytics, Libraries, eCommerce, eCommerce APIs, Third-party APIs, Artificial Intelligence (AI), ChatGPT API, Apollo, Customer Relationship Management (CRM), API Design, API Gateways, Facebook, Social Media Platforms, Social Media Login, AI Chatbots, Chatbots
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