Hi, I'm WitachaiWitachai
I graduated with a degree in Computer Engineering and am passionate about building beautiful, functional web applications. I have experience in fullstack development, machine learning, and enjoy learning new technologies. I am confident, humble, and always open to new challenges.
Who I Am
I graduated with a degree in Computer Engineering from Dhurakij Pundit University. I am passionate about web development, machine learning, and always eager to learn new technologies. I have over 10 years of experience in basic computer maintenance, software installation, and troubleshooting, which has strengthened my technical and problem-solving skills.
I am confident, humble, and open to new challenges. My journey in tech started early, and I enjoy bringing humor into serious situations while staying composed and focused on my goals.
Name:
Witachai Sawatdi
Email:
witachai.official@gmail.com
Location:
Prachuap Khiri Khan, Thailand
Availability:
Available for freelance
Backend Developer (NestJS)
Responsible for enterprise-scale modernization: dismantling and migrating legacy financial, loan, and document systems built on Delphi / InterBase into a new NestJS microservices architecture. Contributed across more than ten internal services spanning backend APIs, service integration, and reporting surfaces.
- Built NestJS REST services for debt tracking, e-contract reporting, auto-loan onboarding, rate lookup, and document workflows.
- Migrated legacy Delphi / InterBase business logic into domain-separated TypeScript modules behind gRPC wrappers.
- Implemented JWT & API-key guards, Redis-backed sessions, and centralized error handling across services.
- Hardened reliability with upstream deadlines, concurrency gates, and documented 503/504 error mapping.
- Standardized observability using OpenTelemetry, SigNoz, and Sentry with sensitive-data masking.
- Containerized services with Docker and verified releases through GitLab CI/CD and targeted Jest suites.
IT Developer (Internship)
Participated in frontend and backend web development for automated document and invoice generation systems.
- Developed responsive web interfaces using React (JSX) for invoice creation and management.
- Integrated PDF document generation libraries and tools including @react-pdf/renderer and jsPDF.
- Collaborated on system architecture, database modeling, and real-world team development workflows.
Grouped by the part of the system I work on.
Backend & Microservices
Designing service boundaries, contracts, and business logic for enterprise systems.
Data & Storage
Modeling schemas, tuning queries, and bridging modern stores with legacy databases.
DevOps & Observability
Shipping containers through CI/CD and keeping services traceable in production.
Security & Integration
Guarding service boundaries with token, session, and rate-limit strategies.
Frontend & UI
Building responsive product surfaces and internal dashboards.
AI, ML & Tooling
Applying models to real business data and pairing with AI dev tools.
Each project below solved a concrete problem. Technology names stay as they are; the descriptions cover the challenge, the approach, and the outcome.
Featured Highlights
Vehicle Inspection & Insurance Management Platform
A real vehicle inspection and insurance business needed one web platform for staff operations and customer self-service while keeping its long-running legacy data intact. I built the platform around an Angular frontend, NestJS API Gateway, gRPC microservices, Redis, and Neon PostgreSQL, with a legacy SQL Server bridge for reading existing data. The system supports staff workflows, customer and LINE LIFF experiences, dashboards, documents, notifications, and hybrid data flows without replacing the existing desktop system.
Executive Reporting Dashboard & BFF (report-dashboard)
Executives needed the report numbers without reading raw API output. I contributed to the Angular dashboard and its Express BFF, adding grouped KPI views, Thai date filtering, drilldown, plus BFF guardrails: rate limits, request IDs, upstream health checks, and a report assistant restricted to whitelisted API tools.
Sales Forecasting System (LSTM Deep Learning)
Small retailers order stock by guessing from last month, so they end up overstocked on slow items and out of stock on the ones that sell. I built a system that reads their sales history and predicts the next period, using an LSTM model because sales depend on the sequence of events over time, not just totals. It scored more accurately than the traditional machine learning methods I compared it against. The model sits behind a web app, so a shop owner sees the forecast as a chart and decides what to restock, instead of reading raw numbers. The research was accepted and presented at NCCIT 2025, a national IT conference in Thailand (proceedings pages 331-336).
FR Flower E-commerce Platform
A production-ready flower storefront built for a real business, with a customer-facing catalog and a protected back-office for managing products, categories, images, reviews, delivery areas, sales channels, and localized storefront content. I built the platform with Next.js, Prisma, PostgreSQL, Cloudinary, and LINE ordering, with validation, automated tests, image upload controls, role-based admin access, backups, health checks, and deployment safeguards.
gRPC File Service (service-file-service)
Every service needed a safe place to store documents and images. I worked on a gRPC service with streaming read and upload that writes to either S3-compatible storage (MinIO) or a persistent Docker volume, using atomic overwrite so a failed write never leaves a corrupted file behind.
Daily E-Contract Reporting Service (report-econtract-service)
Management needed daily contract numbers, but wide date ranges were overloading the legacy database. I built the reporting APIs with summary and detail views, EL/Paper classification, bounded date ranges, per-RPC deadlines, and a concurrency gate that protects the upstream system when many people request reports at once.
I'm actively seeking new opportunities and would love to discuss how I can contribute to your team.
Contact Information
Location
Ngamwongwan 27 Yaek 4, Bangkhen Subdistrict, Mueang Nonthaburi District, Nonthaburi 11000
GitHub
View my projectsAvailable for full-time positions, freelance projects, and collaborations