Johnny Chang

Data Engineer @ GESIS - Leibniz Institute for the Social Sciences

About

Data Engineer | MLOps, DevOps | Backend-Aware Data Systems Builder I'm a data engineer focused on designing scalable data pipelines and infrastructure that power machine learning workflows and real-world analytics. My work blends traditional data engineering with hands-on MLOps/DevOps and practical backend experience—enabling fast, stable, and intelligent data platforms. At GESIS, I built a fault-tolerant web scraping pipeline handling 250M+ records with Airflow, Spark, MongoDB, and set up cluster-wide monitoring with Prometheus and Grafana. I’ve also deployed ML APIs and tracking services (MLflow, Flask) and automated workflows with CI/CD (GitLab) and Ansible. With a background in NLP and experience in web-backend development (Django, Spring Boot, GraphQL), I often bridge the gap between data infrastructure and ML application—from data ingestion and normalization, to inference APIs and user-facing tools. 🛠 Tech Stack Snapshot: ．Programming: Python, Java, SQL, Bash ．Data Infra: Airflow, Spark, MongoDB, Postgres, Docker, Prometheus, Grafana ．MLOps/DevOps: MLflow, Flask API, PyTorch, HuggingFace, Scikit-learn ．Backend: Django, Spring Boot, GraphQL, REST APIs, GitLab CI/CD, Ansible ．NLP Focus: BERT, Transformers, NER, Sentiment Analysis, Text Normalization 📁 GitHub: github.com/poch4319

Country

Germany

City

Cologne

Industry

Computer Software

Skill

Natural Language Processing (NLP), Deep Learning, Machine Learning, Data Science, Translation, Statistics, Research, Artificial Intelligence (AI), Analytical Skills, Python (Programming Language), Photoshop, Microsoft Office, Microsoft Word, Microsoft Excel, PowerPoint, Lightroom, K-Nearest Neighbors (KNN), PyTorch, Matlab, Linux

Experience

Data Engineer

GESIS - Leibniz Institute for the Social Sciences

2023-5 - 2026-1 · 2 yrs 9 mos

Cologne

- Developed a web scraping data pipeline (MongoDB, Airflow, Spark) with data integrity check and fault-tolerant strategy, delivering 250M+ posts as queryable data for analysts with uninterrupted operation since Nov 2023 - Built a web platform backend for researchers in need of programming resource in both Spring Boot, Java (GraphQL), and Django versions, hosting curated repositories for social researchers to incorporate in research - Implemented DevOps practices in web development, replacing manual processes with GitLab CI/CD, automated testing, Docker image builds, and Ansible-based deployments, improving deployment speed and site reliability - Architected Prometheus and Grafana for cluster-wide monitoring, automating error checks with real-time alerts across Hadoop and critical frameworks, enabling immediate issue detection and resolution among teams

NLP Machine Learning Engineer

Shoalter Technology

2022-12 - 2023-3 · 4 mos

Taipei, Taipei City, Taiwan

- Prototyped GPT-Turbo-powered Rasa chatbot template generation, evaluating its potential for automating intent and response creation - Explored prompt learning for entity extraction in chatbots, assessing feasibility and identifying critical limitations in accuracy and integration

Machine Learning QA Specialist

ReadSpeaker

2021-8 - 2022-10 · 1 yr 3 mos

Uppsala County, Sweden

- Analyzed systematic pronunciation errors in TTS outputs, uncovering linguistic patterns for model refinement - Provided linguistic insights on lexicon, tokenization, text normalization, and homograph disambiguation, shaping rule-based improvements in the NLP pipeline - Compiled error distribution statistics, delivering data-driven reports that informed engineers on key areas for enhancement in speech synthesis

Machine Learning Thesis Intern

AstraZeneca

2021-1 - 2021-10 · 10 mos

Gothenburg Metropolitan Area

- Developed a PyTorch reinforcement learning fine-tuning framework for pre-trained Transformer model for molecular optimization, generating 92× more viable drug candidates - Built a custom catastrophic forgetting solution for fine-tuning, reducing erroneous molecular outputs by 17×

Product Marketing Specialist

MSI

2018-3 - 2019-6 · 1 yr 4 mos

New Taipei City, Taiwan

．Project leader for all product materials including wordings, videos and images ．Writer of product public release (PR) for international medias and foreign branches ．Owner of company blog and more than 10 product branding projects for monitors and desktops ．Product ambassador for international medias in award events, exhibition or business fair

Freelance Translator

Self-Employment

2014-5 - 2017-1 · 2 yrs 9 mos

Taiwan

．Chinese and English Translating: Wine company briefings, Cosmetic user experiences…etc ．Transcribing Chinese interview recording into written English

Education

Uppsala University

Language Technology (Computational Linguistics)

2019 - 2021 · 2 yrs

Thesis Topic: ．Improving Transformer-Based Molecular Optimization Using Reinforcement Learning Project: ．Method Exploration: Relation Extraction Using BERT ．https://github.com/gn02172336/Method-Exploration-Relation-Extraction-Using-BERT/blob/main/RD_report_pochun_chang.pdf Probability and Statistics, Natural language Processing, Algorithm and Data Structure, Machine learning and Deep Learning, Data Science, Sentiment Analysis, Information Retrieval, Machine Translation, Text Analysis.

National Chiao Tung University

Foreign Languages, Literatures, and Linguistics

2010 - 2014 · 4 yrs

Linguistics: Phonology, Syntax, Morphology, Semantics, Phonetics Business English Practical/Advanced Translation (Chinese/ English) English Writing Industry Analysis Industrial and Organization Psychology International Relations and Organizations Psychology Film Studies(Horror, Japanese) Philosophy Literature (Chinese, American, English, Ancient Western) Art