Phuong Nguyen Duy - Senior Software Engineer
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About Me

Phuong Nguyen Duy

Senior Full-stack Engineer with 7+ years building in-house SaaS products on .NET and Vue. Currently lead engineer on Mantu's internal product platform serving 8,000+ employees globally, where I own 8+ products end-to-end across roadmap, architecture, delivery, and long-term adoption.

Strong track record of measurable impact: cut API p95 latency 82% (14s → 2.5s), reduced sync-job database load by ~99% (10,000+ queries to 4–5), and led full V1→V2 platform migrations preserving 100% data integrity. Comfortable shipping AI-powered features with Azure OpenAI (tool_calls, structured outputs, RAG/embeddings) and driving cross-team technical handovers.

Open to Senior / Lead roles in product companies.

Ready to Build Products That Matter?

Looking for a Senior or Lead engineer who owns products end-to-end, ships AI-powered features, and delivers measurable performance wins? Let's talk.

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Education & Research

2012 to 2016

B.Sc. Software Engineering

VNU-HCM — University of Science

Research: Vietnamese Automatic Speech Recognition & Speech Separation — contributed to the VN-SpeechMix dataset for Vietnamese speech processing.

Experience

May-2023 to Present

MANTU

SENIOR SOFTWARE ENGINEER — IN-HOUSE PRODUCT TEAM
Team: ITCS — IT Core Services (Internal Product Platform)
Users: 8,000+ Mantu employees globally | Team Size: Up to 10 members
Context: In-house product engineer owning 8+ internal SaaS products (SurveyV2, THOR, ITAccess, HouseOfApps, Location API, MessageHub, XFiles, Guardian, CDN). Full lifecycle ownership: roadmap, architecture, development, deployment, user adoption, and long-term maintenance.
Key Achievements:
  • Survey V2 — flagship product, lead engineer. Owned end-to-end migration from legacy V1 (5+ year-old ASP.NET MVC monolith) to V2 (.NET 8 Clean Architecture with CQRS/MediatR). Preserved 100% data integrity across thousands of historical surveys, responses, and permissions with zero user-reported data loss. Drove product adoption by shipping AI-assisted survey creation (Azure OpenAI tool_calls), reminder-email flows, and in-app notifications. Currently designing RAG / embedding-based semantic caching (text-embedding-3-small) to cut LLM cost while improving question quality.
  • Location API — 82% p95 latency reduction (14s → 2.5s). Parallelized Google Places / Geocoding external calls using SemaphoreSlim-controlled concurrency, reducing tail latency by ~5.6× for an API consumed by 8+ downstream products. Added address-migration background service with telemetry, deduplication, and export. Packaged the UI as a reusable NuGet (Location.UI.Mvc) adopted by other internal teams.
  • Sync-job optimization — ~99% query reduction. Cut 10,000+ database queries per run down to 4–5 by pre-loading lookup sets into Dictionary / HashSet in memory and converting per-row queries to bulk reads. Job runtime dropped from hours to minutes, freeing scheduling capacity for downstream pipelines.
  • THOR (ErpDocument) — reusable component library & lifecycle automation. Built ThorCascader (multi-level folder picker) and ThorSelect Quasar components adopted across multiple modules, accelerating feature delivery for the team. Implemented document template lifecycle automation (expiration reminders, auto-archiving, overdue rejection) via HostedService background workers. Integrated SharePoint CSOM for folder structure sync and ODIN for portal/category management.
  • Production debugging across distributed services using KQL. Root-caused: a FluentValidation concurrent-collection threading bug in ITAccess (parallel validators corrupting Dictionary writes), GDPR delete 403s across Service Bus consumers, MessageHub timeouts, and Guardian multi-branding 500 errors (Unity DI lifetime mismatch) — correlating Application Insights traces across 3–4 services.
  • CDN download service migration. Migrated from .NET Framework 4.8 to .NET 8 Minimal API, including a public file-access statistics dashboard (KQL + charts) supporting millions of records. Fixed 307 redirect loop and ZIP-streaming flow with AllowSynchronousIO.
  • Technical leadership. Authored ITAccess technical handover documentation on Azure DevOps Wiki, enabling another team to take full ownership without ramp-up loss. Active in the team's AI best-practices channel; piloted Claude Code + MCP / Azure DevOps integration to improve team developer experience.
Technologies: Back-end: .NET 8, Clean Architecture, CQRS/MediatR, EF Core, Dapper, Hosted Services, FluentValidation | Front-end: Vue 3, Quasar, TypeScript, Pinia | Cloud: Azure (App Services, Service Bus, Storage, Application Insights + KQL, OpenAI, DevOps Pipelines, Entra ID) | AI: Azure OpenAI (tool_calls, function calling, embeddings), RAG, prompt engineering | Testing: XUnit, NUnit, SpecFlow
Jun-2022 to May-2023

POSITIVE THINKING COMPANY

SENIOR SOFTWARE ENGINEER
Project: McK CostGauge — Diagnostic Tool
Customer: UK client | Team Size: Up to 10 members
Project Description: SaaS diagnostic platform. Transformed Excel-based cost analysis model into a scalable web platform with real-time analytics.
Key Achievements:
  • Refactored legacy monolith toward microservices, enabling independent feature teams to deploy without coordinating releases — improving horizontal scalability and release cadence.
  • Introduced GraphQL alongside REST for diagnostic queries, reducing over-fetching and simplifying frontend query composition.
  • Raised code coverage from 40% to 85% by backfilling unit/integration tests on critical business logic and wiring coverage gates into CI.
  • Optimized Excel import/export with NPOI + Azure Storage streaming, cutting processing time roughly in half for large report uploads.
  • Implemented background processing pipelines using Hangfire for parallel processing of large datasets.
Technologies: Back-end: .NET 6, PostgreSQL, GraphQL, Hangfire, Hasura, Dapper | Cloud: Azure Storage
Jul-2021 to Jun-2022

SAIGON TECHNOLOGY

.NET DEVELOPER
Customer: Idealpos — Australia | Team Size: Up to 7 members
Project Description: Enterprise POS system managing users, invoices, orders, and subscriptions for the Australian retail market. Multi-tenant SaaS platform with comprehensive reporting and third-party integrations.
Key Achievements:
  • Designed a reusable framework-component library that became the default starting point for new modules in the portal, noticeably reducing feature delivery time.
  • Led legacy-codebase refactoring to modern .NET Core 3.1 / Angular 5 standards, paying down technical debt and unblocking further feature work.
  • Authored client-facing documentation and training materials, strengthening client relationship and closing the handover loop.
  • Implemented RESTful API architecture supporting seamless third-party integrations.
Technologies: .NET Framework, .NET Core 3.1, RESTful API, Angular 5, SQL Server, EF6, EF Core.
Aug-2019 to Jul-2021

NASHTECH LIMITED

SOFTWARE ENGINEER → SENIOR SOFTWARE ENGINEER (Promoted Jan 2021)
Projects: TV Benchmarking (Ebiquity — UK, team of 35) & internal management systems
Project Description: Media analytics platform processing TV advertising data for the UK market. Handles massive datasets from multiple broadcasters for cost optimization analysis and advertising effectiveness measurement.
Key Achievements:
  • Mentored 4 fresh graduates through the Golden Rookies program on .NET fundamentals, code quality, and code-review practices — helping them ramp onto production teams.
  • Optimized large-file import pipelines with layered caching strategies, sustaining throughput as client data volumes grew.
  • Built SQL Server ↔ MongoDB synchronization and designed schemas for the benchmarking dataset.
  • Shipped OWASP Top 10 hardening on internal management tools and led technical code reviews for the team.
Technologies: ASP.NET Core 3.1 Web API, SignalR, EF Core (Code First), SQL Server, MongoDB, Angular, Material UI, XUnit, NUnit, Aspose, EPPlus.
Aug-2018 to Jul-2019

DEVINITION SOFTWARE

ASSOCIATE DEVELOPER
Projects: ECO2 (OnePeterson — USA, IoT) & ITJobs (TOG Recruitment — Netherlands)
Team Size: Up to 5 members
Project Description: ECO2 is an industrial controlled-atmosphere system (oxygen reduction via nitrogen flushing) used worldwide for chemical-free pest control in commodity storage. ITJobs is a recruitment platform connecting IT professionals with employers across the Netherlands and Vietnam.
Key Achievements:
  • Built Web APIs, web applications, and SOAP services across two projects on .NET Framework and .NET Core 2.1.
  • Developed IoT features for ECO2, an industrial system used worldwide for chemical-free pest control in commodity storage.
  • Designed databases and built responsive UI, gathered business requirements with clients, and set up CI/CD for deployment.
Technologies: .NET Core 2.1, .NET Framework, EF Core (Code First), SQL Server, SOAP, Bootstrap, HTML, CSS, JavaScript.

Skills

🧠 CORE COMPETENCIES

  • Product Engineering: End-to-end ownership, roadmap, user adoption, long-term maintenance
  • System Architecture: Clean Architecture, CQRS, Domain-Driven Design, Microservices, Event-driven (Service Bus)
  • Performance Optimization: Query reduction, parallelization with concurrency control, caching strategies
  • Technical Leadership: Cross-team handovers, mentoring, code reviews, technical documentation
  • Production Debugging: Distributed tracing, KQL diagnostics across multiple services

⚙️ BACKEND TECHNOLOGIES

  • .NET Ecosystem: .NET 8 / 6 / .NET Framework 4.8 (7+ years experience)
  • Web APIs: ASP.NET Core, Minimal API, RESTful, GraphQL, SignalR
  • ORM & Data Access: Entity Framework Core, Dapper, LINQ
  • Architecture Patterns: Clean Architecture, CQRS/MediatR, FluentValidation, State Machine
  • Background Processing: Hosted Services, Hangfire, Azure Service Bus

🤖 AI / ML INTEGRATION

  • Azure OpenAI: tool_calls, function calling, structured outputs
  • Embeddings & RAG: text-embedding-3-small, semantic caching, vector retrieval
  • Prompt Engineering: Structured output design, prompt revision via test harnesses
  • LLM Product Features: AI-assisted content generation, summarization, semantic deduplication
  • AI Tooling: Claude Code, MCP, agentic workflows for developer productivity

💻 FRONTEND & LANGUAGES

  • Vue 3 + Quasar: Advanced — Pinia state management, reusable component library design
  • TypeScript: Proficient — modern ES6+, type-safe APIs
  • Angular 2+: Proficient — SPA, Material UI
  • HTML/CSS/Tailwind: Advanced — responsive design
  • Languages: Vietnamese (native), English (professional working proficiency)

🗄️ DATABASES

  • SQL Server: Advanced — performance tuning, index optimization, schema migration, deadlock debugging
  • PostgreSQL: Proficient — complex queries, data modeling
  • MongoDB: Intermediate — NoSQL design, aggregation pipelines, SQL ↔ NoSQL sync
  • MySQL: Intermediate

☁️ AZURE & DEVOPS

  • Azure Services: App Services, Service Bus, Storage, Application Insights, OpenAI, Entra ID
  • Observability: KQL diagnostics, distributed tracing, structured logging
  • CI/CD: Azure DevOps Pipelines, automated deployment, NuGet package distribution
  • Auth & Security: OAuth 2.0, OpenID Connect, Entra ID / Azure AD, multi-tenant authentication, OWASP Top 10
  • Tools: Git, Docker, Postman, AutoMapper, NPOI

Contact

Phuong Nguyen Duy

Senior Software Engineer — .NET 8 + Vue 3 + Azure

phuongnd.tech@gmail.com

+84 979 891 673

Ho Chi Minh City, Vietnam