Building scalable systems

Yuejia (Roger) Guo.

Software engineer crafting

backend services.

Computer Science and Data Science at the University of Waterloo. I design reliable backend systems, data pipelines, and API-driven applications — from regulatory ingestion at scale to LLM-powered tooling that turns messy workflows into production software.

Waterloo, Canada (437) 818-9423 Open to software engineering opportunities
BACKEND
DATA PIPELINES
AUTOMATION
AI AGENTS
scroll
01

About me

I build backend systems where reliability meets intelligent automation.

I am a Waterloo Computer Science and Data Science student with a 3.9 GPA, focused on backend engineering, scalable data pipelines, and API-driven applications across Python, TypeScript, C++, and SQL.

At Capsule AI, I engineer production ingestion systems for life-sciences data across hundreds of heterogeneous sources — press releases, investor events, scientific literature, and regulatory feeds (NMPA and CDE are two of the newest we added). The core of my work is the automation around them: an AI-assisted onboarding pipeline that discovers, configures, validates, and ships a new company's scrapers with minimal hand-tuning, and a triage-and-debug system that detects extraction failures, isolates the root cause, and proposes the fix — keeping 500+ sources healthy without one-off maintenance.

Previously at Sanofi, I rebuilt fragmented analytics into a unified Snowflake and Power BI platform, cut dashboard load times by over 70%, and prototyped LLM interfaces that let non-technical stakeholders query enterprise KPIs in natural language.

current_focus.json● ● ●
const focus = {
  backend: ["NestJS", "REST APIs", "Redis"],
  data: ["pipelines", "scraping", "ETL"],
  principle: "make systems scale"
};
500+companies scraped
50+companies onboarded / day
20xonboarding throughput gain
PythonTypeScriptC++NestJSNext.jsNode.jsPlaywrightRedisMySQLSnowflakeREST APIsDockerLLMsGemini PythonTypeScriptC++NestJSNext.jsNode.jsPlaywrightRedisMySQLSnowflakeREST APIsDockerLLMsGemini
02

Education

Computer science, statistics, and systems — grounded in practice.

W

University of Waterloo

Bachelor of Computer Science, Data Science

Honours Co-operative Program · GPA 3.9 / 4.0 · Excellent Standing · Term Distinction

Data StructuresOperating SystemsDatabase SystemsSystems ProgrammingComputer ArchitectureApplied Linear ModelsComputational Statistics
03

Work experience

From enterprise analytics to production ingestion at scale.

Remote

Software Engineering Intern

Capsule AI

CURRENT

Built and hardened production data-ingestion systems for life-sciences intelligence — spanning regulatory records, scientific publications, press releases, investor events, and company onboarding at scale.

  • Engineered a multi-layer NMPA/CDE regulatory ingestion pipeline across four NestJS modules and nine Playwright routes, handling anti-bot defenses, JavaScript-rendered pages, nested result views, popup and PDF documents, inconsistent metadata, bilingual entity matching, and extraction fallbacks.
  • Developed Publication Watch, a seven-source scientific-literature tracking system with fault-isolated parallel retrieval, cross-source deduplication, and a Gemini-powered natural-language query compiler with deterministic fallback behavior.
  • Refactored company onboarding from one-off, company-specific scraper development into an AI-assisted batch workflow — increasing effective throughput by 20x+ and enabling validation and onboarding of 50+ new companies per day.
  • Applied and hardened reusable scraper architectures across 500+ distinct companies, adapting extraction, pagination, validation, and failure-handling strategies to heterogeneous websites and data platforms.
NestJSPlaywrightTypeScriptGeminiWeb ScrapingAI Agents
Toronto, ON

Data Analytics Co-op (Portfolio+)

Sanofi Digital Data & AI

Rebuilt a fragmented reporting ecosystem into a unified analytics platform serving multiple business units across Sanofi's digital portfolio.

  • Redesigned data models and backend KPI computation logic to improve consistency across business units, replacing Excel-based workflows with Snowflake and automated Power BI refresh pipelines.
  • Developed scalable ETL pipelines using Snowflake and SQL to automate data ingestion and transformation, reducing manual processing effort by 40%.
  • Optimized query performance and data access patterns, cutting dashboard load times from roughly 5–10 minutes to under 2 minutes — a 70%+ improvement.
  • Implemented validation and processing logic across 100k+ record datasets to ensure consistency and reliability at scale.
  • Prototyped an LLM-powered querying interface for natural-language access to structured enterprise data, improving accessibility for non-technical stakeholders; won 1st place in an internal hackathon.
SnowflakePower BIPythonSQLLLMsETL
Remote

Business Planning & Operations Intern

Visa Inc.

Analyzed international-student credit-card application behavior and built an end-to-end data pipeline to turn survey responses into actionable business insights.

  • Built a Python pipeline integrating the Google Forms API with automated preprocessing scripts for survey data collection and cleaning.
  • Processed and analyzed 2,000+ survey responses, identifying key behavioral patterns and improving reporting accuracy by 25%.
  • Designed interactive Tableau dashboards and a written strategy report to support business decision-making and improve insight delivery efficiency.
PythonTableauAnalyticsGoogle Forms API
04

Selected projects

Systems that ingest, process, and deliver data at scale.

02
AI PRODUCT2026

CoopPilot

A full-stack AI job-matching platform for WaterlooWorks that processes 1,000+ postings, parses unstructured descriptions into structured features (skills, requirements, experience levels), and scores fit using contextual signals beyond keyword overlap — improving matching precision by 30%.

Next.jsLLMsREST APIsStructured Output
03
BACKEND DESIGN2025–2026

URL Shortener Service

A backend system design project supporting high read/write traffic with hash-based unique ID generation, RESTful encode/decode APIs backed by MySQL, and Redis cache-aside caching that cut average response latency by 50%.

MySQLRedisREST APIsSystem Design
04
1ST PLACESanofi Hackathon

Data Quality Classification System

A prototype that identifies and classifies enterprise data-quality issues using rule-based logic, returning structured outputs with issue categorization and recommended resolution workflows for stakeholder routing.

Rule EngineData QualityStructured Output
05
SYSTEMS2026

Backend & System Design Practice

Built RESTful services and simulated high-concurrency load to study backend behavior under pressure — applying Redis cache-aside caching to cut database latency, distributed locking and token-bucket rate limiting for safe concurrent requests, and TCP client-server programs in C++ for low-level connection handling.

C++RedisConcurrencyRate LimitingTCP
06
DATA STRUCTURES2024

LRU Cache (C++)

Implemented a least-recently-used cache with O(1) get and put using a hash map backed by a doubly linked list, mirroring Redis-style eviction policies — then optimized access patterns to improve cache hit rate across test scenarios.

C++Hash MapLinked ListO(1)
07
C++ · GAME2024

Tetris Engine (C++)

Built a complete Tetris game in C++ with an ADT-based design — implementing piece rotation logic, collision detection, and scoring. Hardened stability by debugging memory and pointer issues with GDB and Valgrind, eliminating leaks.

C++ADTsGDBValgrind
05

Contact

Let’s build something reliable, scalable, and ambitious.

I am interested in backend engineering, data systems, AI automation, and graduate-study conversations.