Portfolio

Oscar Solideo Siregar

Software Engineer

Learning is a process that never ends.

About

Software Engineer with solid experience building API-driven systems using Golang and TypeScript. I focus on data flow, API integration, and system reliability — building backends that are scalable, maintainable, and easy to reason about.

Currently expanding into frontend with TypeScript and JavaScript, bridging backend architecture with modern UI to deliver solutions that are both performant and user-focused.

Skills & Expertise

Technologies and tools I work with — from backend systems to databases, security, and infrastructure.

Backend Development

Golang, RESTful API Design, Microservices Architecture, Node.js, TypeScript

Frontend Development

ReactJS, JavaScript (ES6+), HTML5, CSS3, Bootstrap

Databases & Messaging

MySQL, PostgreSQL, MongoDB, Redis, Elasticsearch

DevOps & Tools

Docker, CI/CD Pipelines

Authentication & Security

LDAP, SSO Integration, JWT

System Design

Clean Architecture, Scalable APIs, Concurrent Processing

Experience

Freelance Software Engineer (Fullstack)

Self-employed· Freelance

Jun 2025 – Present · 10 mos

Jakarta, Indonesia · Remote

Delivered full-stack web solutions for multiple clients, developing modern user-facing interfaces and supporting backend services.
Built responsive frontend features using TypeScript and JavaScript with strong focus on clean component architecture and seamless API integration.
Designed and implemented backend services to support frontend requirements, ensuring consistent data flow and system reliability.
Collaborated directly with clients to gather requirements and translate business needs into production-ready technical solutions.
Applied clean architecture principles, testing practices, and structured version control workflows to deliver scalable and maintainable applications.

Backend Engineer

Pinjam Modal | PT Finansial Integrasi Teknologi· Full-time

Oct 2022 – May 2025 · 2 yrs 8 mos

Tangerang, Banten, Indonesia · On-site

Developed and maintained core financial systems for a B2B P2P lending platform, supporting high-volume transactional workflows with strong emphasis on data accuracy and auditability of fund flows.
Designed and implemented disbursement and scheduled payment systems, integrating with multiple Indonesian banking providers to ensure reliable and secure financial processing.
Built end-to-end insurance workflows including registration, premium payments, claims handling, and lender repayment integration with external insurance providers.
Improved system reliability and operational efficiency through performance optimization and application of Clean Architecture principles, maintaining ~90% unit test coverage.
Developed reporting and data export features to support operational monitoring and financial analysis for internal finance teams.

Back End Developer

SALT· Full-time

Feb 2022 – May 2023 · 1 yr 4 mos

Jakarta, Indonesia · On-site

Delivered fintech and enterprise web applications for PT Telkom Indonesia, contributing to improved system efficiency and reliability.
Designed and developed API-driven backend services using Golang and Node.js (TypeScript) to support CMS and user-facing applications.
Built a CMS platform from scratch using KeystoneJS v6, enabling structured and scalable content management.
Improved application performance through Redis caching, significantly reducing content load time.
Implemented secure authentication systems including social login and LDAP integration.
Designed asynchronous processing workflows using RabbitMQ to handle complex survey logic and large-scale data processing.
Applied Clean Architecture principles and TDD practices, achieving ~90% unit test coverage and maintaining high code quality standards.

Education

Bachelor of Engineering, Electrical Engineering

Diponegoro University

Aug 2016 – Apr 2021

GPA: 3.90 / 4.00

Focused on Control Systems in manufacturing environments, studying system stability, feedback control, and automation processes. Developed strong analytical thinking and structured problem-solving skills applicable to complex engineering systems.

Selected Work

GolangPostgreSQLRabbitMQClean Architecture

Fast and Reliable LIMS

A scalable Laboratory Information Management System (LIMS) built with Golang, PostgreSQL, and RabbitMQ. The system manages laboratory workflows from order entry to result reporting, including specimen tracking, worklist orchestration, QC monitoring, audit trails, and role-based access control. Designed with event-driven architecture to ensure high reliability and performance in high-volume laboratory environments.

GolangPostgreSQLHexagonal Architecture

Remuneration Management System – Poltekkes Tanjung Karang

A private institutional remuneration management system developed for Poltekkes Tanjung Karang. The system manages performance-based compensation calculations, attendance integration, KPI aggregation, and structured approval workflows. I was responsible for backend development, including business logic implementation, database schema design, and secure role-based access control.

GolangPostgreSQL

Transactional Point of Sales System

Built backend architecture for a Point of Sales (POS) system focused on transactional integrity and real-time inventory synchronization. Implemented atomic transaction handling, sales aggregation reporting, and stock movement tracking to ensure data consistency across concurrent transactions.

Node.jsPostgreSQL

Employee Management System

Developed backend services for an Employee Management System designed to support HR operations, including employee data management, attendance tracking, role assignment, and structured reporting. Focused on secure role-based access control and scalable API design to ensure reliable HR data management.

Blog

Loading posts...