Julien Le Dem
Principal Engineer at The Apache Software Foundation
Berkeley, California, United States
Summary
🤩
Rockstar🎓
Top SchoolJulien Le Dem is a Principal Engineer based in Berkeley with 15+ years designing and shipping large-scale data systems and open source infrastructure. He co-created OpenLineage and helped found Parquet and Arrow, contributing deep protocol and format work spanning Parquet, Arrow, Iceberg and Marquez that power modern analytics pipelines. A consensus-driven technical leader and mentor, he excels at clarifying architecture, producing high-quality code, and giving constructive, detail-oriented reviews that help teams move faster. Julien blends hands-on back-end and systems-level craftsmanship (format specs, IPC schemas, encoding optimizations) with community leadership as an Apache PMC member and project chair. He favors pragmatic, peer-oriented collaboration and has a track record of turning research ideas (Dremel-inspired columnar storage) into widely adopted production standards.
15 years of coding experience
24 years of employment as a software developer
Mathematics Physics, Mathematics Physics at CPGE Pierre Corneille RouenLycee les Fontenelles, LouviersMSc / diplome d'ingénieur Computer Science, MSc / diplome d'ingénieur Computer Science at Institut Supérieur d'Informatique Modélisation et leurs Applications
French, English
Stackoverflow
51reputation
2kreached
1answer
0questions
Github Skills (66)
testing10
metadata10
file-format10
apache-arrow10
javas10
encoding10
parquet10
schema10
openapi10
javascript10
client-library10
aggregator10
big-data10
data-serialization10
data-storage10
Programming languages (12)
Github contributions (5)
apache/parquet-format
Jan 2013 - Jan 2020
Apache Parquet Format
Role in this project:
Back-end Developer
Back-end DeveloperContributions:15 reviews, 85 commits, 7 PRs in 7 years 1 month
Contributions summary:Julien primarily contributed to the Apache Parquet format definition files. Their work involved modifying the Thrift IDL files, adding new data types, and refactoring the dictionary encoding. They improved the metadata handling, added statistics, and implemented a new data page type. Additionally, the user added a utility class to hide Thrift and updated the changelog, demonstrating a strong understanding of the Parquet file format's internal structure and its evolution.
avroparquetapachebig-dataapache-parquet
apache/parquet-java
Jan 2015 - Aug 2024
Apache Parquet Java
Role in this project:Back-end Developer
Back-end DeveloperContributions:5 reviews, 11 PRs, 3 pushes in 9 years 9 months
Contributions summary:Julien's commits primarily focus on refactoring code to use indices instead of field names, streamlining the process of reading and writing data within the Parquet format. They further enhanced the data storage by integrating support for decimal values with the aid of the existing Binary object, while also integrating new values to the page level encoding. The user also addressed bugs associated with handling empty fields.
avroparquetapachebig-dataapache-parquet
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