Duy T. Nguyen
Backend Engineer · Systems Thinking · Decision Science
Understanding Systems.
Making Better Decisions.
Sharing What I Learn.
Backend engineer working on identity, data-intensive services, caching, and reliable systems. I document the engineering decisions, experiments, and trade-offs behind what I build.
BackendTypeScript · Node.js · NestJS · REST APIs
DataPostgreSQL · Redis · MongoDB · Neo4j
SystemsDocker · IAM · Caching · Reliability
SeekingJunior Backend / Software Engineering roles
Selected Work & Evidence
View All Work →Multi-Tier Permission Hierarchy
Backend Engineering · IAMTypeScript · NestJS · Redis · Neo4j · MongoDB · Docker
Problem: Recursive authorization evaluation across 6-level role hierarchies pushed p99 latency above 32 ms.
Decision: Introduced a three-tier read cascade (Redis L1 → Neo4j → MongoDB) with transactional outbox event invalidation.
Evidence: Slashed p99 latency to <2 ms at 350 req/s in reproducible K6 benchmarks.
Zero-Trust Cryptographic Key Engine
Systems & Security · KMSTypeScript · Rust · SoftHSM2 · PKCS#11 · Docker · JWT (ES256K)
Problem: Shared symmetric secrets created a whole-platform blast radius, while direct HSM signing bottlenecked at 1,200 ops/s.
Decision: Engineered hardware-backed envelope encryption with 64-byte ES256K compact signatures and 4-phase zero-downtime JWKS rotation.
Evidence: Achieved 108,500 ops/s host signing throughput and <0.05 ms zero-roundtrip edge verification.
Adaptive Load Balancing with Multi-Armed Bandits
Decision Science · Operations ResearchPython · Multi-Armed Bandits · Monte Carlo Simulation · Non-Stationary Environments
Problem: Static routing heuristics (Round-Robin, Least-Connections) fail to adapt when microservice latency drifts under non-stationary loads.
Decision: Benchmarked five Multi-Armed Bandit algorithms (UCB, TS, SW-UCB, D-UCB) over 150 Monte Carlo trajectories with equal-budget hyperparameter tuning.
Evidence: Reduced mean request latency from 51.9 ms to 18.6 ms, while documenting empirical policy rank reversals.
Technical Notebook & Knowledge Graph
Cross-references between architecture case studies, atomic engineering notes, and research.
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Currently Exploring
Distributed coordination & consensus
Adaptive systems & online learning
Reliability under non-stationary workloads
Decision-making under uncertainty
On Signaling · Why This Workspace
Read Essay →Technical competence is difficult to observe directly from a resume alone. This site is built as a public engineering workspace to document real architectural choices, constraints, trade-offs, and empirical benchmarks—providing verifiable evidence rather than ungrounded claims.