Do Xuan Loc.
ENVIJA

Experience

From building features to shaping systems.

The roles, projects, and engineering decisions behind my work.

Current focus · October 2026

Closer to the real operating conditions.

Recent work connects AI evaluation, security verification, and agent tooling to the way people use systems.

Production AI evaluation

Recording quality, transcription, diarization, and speaker roles—evaluated together with the downstream workflow.

Security verification

Trace findings to evidence, inspect release risks, and make the next action clear for the engineering team.

AI product operations

Photo and listing-copy workflows, data synchronization, storage lifecycles, and cloud cost.

Agent tooling & privacy

Local developer workflows, tool permissions, session history, and careful handling of information in logs.

Career & selected projects

2025 — Present

Valixara

Founder & CEO · Principal Engineer

Remote · Ho Chi Minh City

Xem IDE · v1.0.3

A macOS workspace for projects, AI sessions, and an inspectable action history. Built for working across repositories without losing context.

Contributions & technical details
  • Multi-pane workbench combines project context, AI conversations, and repository work in one desktop workspace.
  • Restores conversation history when continuing a session, so the visible UI retains context alongside the agent.
  • Keeps project knowledge in workspace Markdown and uses SQLite as a derived local index.
  • Records AI actions in an append-only hash-chained ledger; file access is scoped to workspace roots.
RustTauri 2React 19TypeScriptSQLite (WAL)

Project-Intelligence Knowledge Platform

A Project-Intelligence OS: RAG + knowledge graph over enterprise context, answerable in natural language with an immutable audit trail of what the AI did.

Contributions & technical details
  • Chose Postgres + pgvector over Neo4j / Pinecone to keep relational and vector data in one store with native joins and $0 infra overhead — logged with the recall threshold that would falsify the choice
  • Picked HNSW over IVFFlat for incremental inserts without a training step; made the chunk (not the document) the retrieval unit
  • Origin of the hash-chain primitive later re-implemented in Rust in the Cockpit
PythonPostgres + pgvector (HNSW)Claude answererStructured extractionSHA-256 audit chain

06/2023 — Present

MarketEnterprise Vietnam

Tech Lead · AI & Systems Architecture

Ho Chi Minh City

Call Recording Intelligence Pipeline

Turns call recordings into searchable Japanese summaries + a structured analytics warehouse, so purchasing staff stop re-listening to whole calls for context.

Contributions & technical details
  • Built an event-driven pipeline (S3 → SQS → SageMaker async → SNS → batch) running self-hosted Whisper Large-v3 + NeMo diarization plus structured extraction — insourcing ML deleted external AI-vendor dependencies, a privacy win for a business handling customer PII
  • Cut LLM cost with in-context batching (Pydantic-array output ≈ 80% fewer prompt tokens) and treated the model as untrusted: rejecting transcripts whose timestamp count drifts outside a bounded ratio
  • Decomposed a large monolith into least-privilege read/write/feedback microservices; documented the async-202-poll pattern with its real gotchas (SQS visibility buffer, DynamoDB eventual-consistency)
  • Recent focus: recording compatibility, transcription quality, hallucination checks, diarization, and speaker-role evaluation across the actual workflow.
Python 3.11AWS SAMSageMakerS3 Tables / IcebergReact 19X-Ray

Omnichannel Trade-In AI Agent

An omni-channel (LINE / WhatsApp / Telegram / Web) multi-agent system that buys back used electronics end-to-end — dynamically discovering which specs matter per product instead of hardcoding question trees.

Contributions & technical details
  • Fused LLM flexibility with deterministic domain truth: the model proposes a per-product schema, then a hand-curated hardware-spec table forbids impossible fields
  • LangGraph supervisor + specialist nodes; structured output everywhere with retry/backoff
  • A real P99 tail-latency investigation (45s = 11.5× P50) drove schema-cache pre-warming and a circuit breaker; HITL gating on payout
LangGraphGemini 2.5 (multimodal)Bedrock KB RAGPostgres checkpointerE2E AI-simulator

Call Automation Platform & Japanese Voicebot

A multi-tenant outbound/inbound call-automation platform: auto-dial on CRM events, throttled bulk campaigns, and a Japanese inbound voicebot for product registration.

Contributions & technical details
  • Protected the carrier with an EventBridge → SQS → Lambda rate-limiter and a bounded retry state machine (max 5, then FAILED) that deliberately stops harassing customers
  • Voicebot pairs Amazon Lex V2 (ja_JP) with Bedrock Claude Haiku for dynamic question generation; hardened with spam / dead-air / duration guards
  • Handled real telephony failure modes: dead air, brand misrecognition, PostCode format; incomplete-save on early hangup
Python 3.13AWS SAMLex V2 (ja_JP)Bedrock (Claude Haiku)DynamoDB Streams → Kinesis → S3

AI-Assisted Security Review Harness

An AI security-review harness where only findings backed by machine-verifiable proof block CI — verdicts are assigned by code, not by an LLM.

Contributions & technical details
  • The centerpiece is a pure-Python proof gate that recomputes every verdict and discards whatever an LLM set: a SAST static trace alone returns 'unconfirmable' and must escalate to a live PoC
  • Chose LangGraph over CrewAI because CrewAI 'trusts the LLM's word' with no place for a non-LLM decision node
  • Drove cost to a <50k-tokens/scan target by letting scanners do the heavy lifting; reports signed with in-toto/DSSE
  • Recent focus: trace findings to reproducible evidence and assess release risks before recommending engineering actions.
LangGraphLiteLLMSemgrepTrivyGitleaksNuclei

Listing Photo & Copy Generation

Two cost-bounded inference products: batch background-removal for listing photos, and SEO-optimized Japanese listing copy with cited specs.

Contributions & technical details
  • Photo pipeline: a custom-trained BiRefNet matting model behind a Florence-2 VLM pre-filter that decides whether removal is even needed; GPU endpoints autoscale on SQS queue depth and stop when idle
  • Reserved concurrency matches an external API's RPM ceiling (backpressure, not crashes)
  • Copy pipeline: JSON-schema-constrained Gemini output (Zod → responseSchema → re-validate) with content-hash prompt caching and in-flight dedupe
  • Recent focus: photo and copy workflows, data synchronization, storage lifecycles, and cloud cost control.
Next.js 15AWS SAMSageMaker asyncBiRefNet / Florence-2S3 → SNS → SQS + DLQTypeScript

Platform Modernization — Monolith → Microservices

Redesigned a large used-goods trading platform from monolithic to microservices, optimizing performance and letting teams ship independently.

Contributions & technical details
  • Applied NX Monorepo with explicit boundaries between internal services and public APIs — boundaries as structure, not convention
  • NestJS microservices following SOLID with stable contracts; per-environment CI/CD on AWS (EC2 + CodePipeline)
  • Event-driven notification architecture (SQS & Lambda), with MySQL query and index optimization
NX MonorepoNestJSNext.jsAWS (EC2, ECR, SQS, Lambda, CodePipeline)MySQL

09/2022 — 04/2023

PloggMedia

Web Developer (Remote)

Remote

Bucco (Healthcare SaaS — France)

Maintenance and feature development for an application connecting dental clinics in the French market.

Contributions & technical details
  • Full-stack development with NestJS, Vue.js, and Vuetify
  • Improved UI/UX and fixed bugs based on real user feedback
  • Developed asynchronous collaboration skills with a European team
NestJSVue.jsVuetifyVuexDocker

Synode (3D Instructions SaaS)

Developed a SaaS platform for creating and sharing interactive 3D assembly instructions, replacing manual 2D documents.

Contributions & technical details
  • Integrated 3D display on the web to replace 2D CAD documents
  • Converted Figma designs to real interfaces and built backend APIs
  • Combined Three.js, Strapi, and NestJS in a Docker environment
NestJSThree.jsVuetifyStrapiDocker

04/2022 — 06/2022

GenCapital

Frontend Developer

Ho Chi Minh City

Crypto News & E-learning Platform

Built interfaces for a cryptocurrency market learning and news platform.

Contributions & technical details
  • Connected APIs to display on-chain data and supported technical documentation
  • Optimized user experience across multiple devices
  • Developed learning progress tracking modules
ReactUI/UXResponsive Web

Beyond the day job

Independent builds.

2026 — present

doxuanloc.space — self-updating portfolio

An Astro site that behaves like a content product: a multi-AI pipeline publishes a daily post + auto-syndicates to LinkedIn, gated by a build-blocking JSON-schema + security validator that fails the deploy on missing fields, bad sources, or leaked internal names. Scroll physics chosen from measured jank, not convention.

Astro 5Trilingual EN/VI/JAMulti-AI pipeline
live

2025

Xuân Lộc Solar — agri-EPC business site

Repositioned a business from unit economics — commodity solar retail → higher-ticket agricultural EPC + O&M — not aesthetics. Deleted fabricated social-proof counters and relabeled stock photos honestly; tuned accessibility (18px/1.7, big tap targets) for older rural buyers.

Vanilla HTML/SCSSVercel edge

2025

BĐS Bảo Lộc — real-estate platform

A hybrid CMS where the data model is designed around a constraint first: owner PII can never reach the client. Fail-safe auth blocks admin routes on misconfig; wrote its own production-readiness audit and refused to ship on P0 findings.

Next.js 15Payload CMSSupabaseS3

2022-10 — 2023-11

NauPhaChe — Bartending Course Platform

Personal project building a course management platform: payments, activation-code distribution, and content management.

Next.jsBootstrapNestJSMongoDB
client admin

2023-03 — 2023-05

MyReview — Viettel (Myanmar)

Web interface development for an entertainment platform, integrating OTP authentication via the Mytel carrier.

HTML5CSSExpressJSTypeScript
site

Education

The foundations.

2018 — 2021

University of Information Technology (UIT)

Vietnam National University, Ho Chi Minh City

Computer Engineering

2021 — 2024

BTEC FPT

FPT Education

Software Engineering