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Software EngineerFull-Stack DevelopmentBackend & Data Engineering

Walter Marroquin

  • San Salvador, El Salvador
  • walter.marroquin.herrera@gmail.com
  • waltermarroquin.com
  • linkedin.com/in/walter-marroquin

01Professional Summary

Software Engineer with 5+ years of professional experience building and optimizing software across frontend, backend, data processing, and infrastructure. Currently develops full-stack products with Next.js, NestJS, PostgreSQL, Docker, and AWS, using an agentic engineering workflow with Claude and AI agents. Strongest in backend performance and maintainable architecture: cut a production API's response time from ~10 minutes to under 3 seconds. Also brings data engineering experience as tech lead of a multi-source ETL platform, and technical leadership from growing into an L5 engineer who led developers and evaluated engineering candidates. Works daily in English with international teams.

02Technical Skills

Languages
TypeScript, JavaScript, C#, Java, Python, SQL, HTML5, CSS
Frontend
React, Next.js, Angular, RxJS
Backend
NestJS, .NET / .NET Core, Spring Boot, Spring Batch, Spring Security, FastAPI, REST APIs, Keycloak (SSO)
Databases
PostgreSQL, Microsoft SQL Server, relational data modeling
Cloud & DevOps
AWS, Docker, Kubernetes, CI/CD, Jenkins, Git
Observability & Analytics
Datadog, Google Analytics, Firebase Analytics
Data Engineering
ETL pipelines, batch and parallel processing, data validation and standardization
Engineering Practices
Design patterns (Factory, Strategy), performance optimization, refactoring, code review, functional validation, Agile Scrum
AI-Augmented Development
Agentic engineering with Claude and AI agents, reusable Claude skills

03Professional Experience

  1. DesignliSoftware Developer

    Jan 2026 – PresentRemote

    • Build full-stack product features with Next.js on the frontend and NestJS on the backend, backed by PostgreSQL, covering APIs, data models, and complex business logic.
    • Develop configurable form workflows with conditional visibility, filtering, and validation rules that support complex product configurations and their dependencies.
    • Contribute to deployment and DevOps work with Docker and AWS across the delivery lifecycle.
    • Apply agentic engineering across the software development lifecycle, using Claude and AI agents to refine user stories, define technical specifications, implement features, review code, and validate functionality.
    • Initiated reusable Claude skills that standardize documentation for developers, AI tools, and pull requests, laying the groundwork for consistent AI-assisted practices across the team.
    • Review pull requests and validate implementations against requirements.

  2. NICE (formerly ClearView El Salvador)

    Sep 2023 – Dec 2025Remote

04Education

B.S. in Computer Systems Engineering (Ingeniería de Sistemas Informáticos)

Universidad de El Salvador · 2021

05Certifications

  • Data Engineering Foundations Professional CertificateAstronomer2025
  • Docker Foundations Professional CertificateDocker, Inc.2025
  • JavaScript Foundations Professional CertificateMozilla2025
  • Learning SQL ProgrammingNASBA2025
  • EF SET English Certificate 65/100 (C1 Advanced)EF SET2022

06Languages

Spanish
Native
English
C1 Advanced (EF SET), used daily with international teams

Full-stack development of gamification features for a large-scale contact center platform, including games such as Battle Boat and Shadow Boxing, challenges with real-time feedback, user metrics dashboards, and CSV/Excel data export. Joined through ClearView El Salvador and stayed with the same team and product after its acquisition by NICE. In both roles, also tested and validated teammates' work before release.

Software EngineerJan 2025 – Dec 2025

  • Reduced a game-history API's response time from ~10 minutes to under 3 seconds by removing an unnecessary game simulation and computing player results directly from existing database records. Presented the investigation, root cause, and solution to teams across the company.
  • Refactored game execution logic with the Factory and Strategy patterns, isolating each game type behind a common interface so new games could be added without modifying existing logic. This cut estimated new-game development effort by 15%+.
  • Developed features end to end in Angular and .NET Core, spanning UI, backend services, and SQL Server queries.
  • Reviewed pull requests for quality, maintainability, and adherence to project conventions.

Software DeveloperSep 2023 – Dec 2024

  • Built gamification features with Angular and RxJS on the frontend and C#/.NET on the backend, using RxJS data flows to keep game state and player results in sync with backend services.
  • Wrote and maintained SQL Server queries for game results, player scoring, and rankings.

  • OnLifeSoftware Developer

    Mar 2023 – Mar 2024Freelance, part-time · Remote

    • Built and maintained frontend functionality for a web application with Next.js and TypeScript in an Agile Scrum team, using Jenkins in the build and deployment workflow.
    • Integrated BigCommerce for e-commerce and purchase flows, and managed content with WordPress.
    • Integrated and validated Google Analytics and Firebase Analytics, then ran an initial analytics study of usage patterns and reach.

  • Applaudo StudiosSoftware Engineer (L5) · Frontend Developer

    Feb 2021 – Sep 2023Remote

    Hired as a Frontend Developer and promoted to Software Engineer (L5), expanding ownership across frontend, backend APIs, and observability for e-commerce, hospitality, and machine learning client projects.

    • Implemented Datadog from scratch across frontend and backend on a Holiday Inn project, enabling proactive error detection and reducing production error investigation from hours to minutes.
    • Led a team of 2 developers, guiding technical decisions and code quality.
    • Conducted 15+ technical candidate evaluations focused on programming fundamentals and software engineering knowledge.
    • Developed API endpoints with Python and FastAPI, beyond the primary frontend scope.
    • Supported Docker and Kubernetes configuration for deployment and monitoring.
    • Integrated the frontend with backend APIs for an ML-powered résumé evaluation system.
    • Built frontend features with React and Next.js, including an online pharmacy platform, and reduced redundant requests through refactoring and caching strategies.

  • DIGESTYCFull Stack Developer (Tech Lead)

    Oct 2019 – Sep 2020Freelance · Remote

    Data integration platform for El Salvador's national statistics office (Dirección General de Estadística y Censos).

    • Led a four-person development team as tech lead, overseeing task delegation, code reviews, and delivery against project goals and deadlines.
    • Built ETL pipelines with Java, Spring Boot, and Spring Batch to extract, transform, validate, and standardize large datasets from Excel, TXT, JSON, CSV, DBF, and SPSS sources.
    • Designed a flexible relational data model in SQL Server to store varying, initially unknown data structures.
    • Implemented scheduled, unattended batch jobs with parallel processing of large datasets.
    • Built error capture that separates retryable failures from cases requiring human review, and used transactions with rollback to keep data consistent on failure.
    • Built reports with JasperReports. The stack also included Spring Security, Docker, and Thymeleaf.

  • Banco Central de Reserva de El SalvadorSoftware Developer Intern

    Feb 2020 – Aug 2020San Salvador

    • Configured a Docker and Kubernetes server environment for application deployment as part of an architecture proof of concept.
    • Integrated Keycloak for centralized authentication and Single Sign-On (SSO).
    • Set up an automated deployment workflow triggered by repository pushes (CI/CD).
    • Built a Spring Boot proof of concept to validate the architecture and service/infrastructure integration.