Valentin Lehuger, Developer in Paris, France
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Valentin Lehuger

Verified Expert  in Engineering

Software Developer

Location
Paris, France
Toptal Member Since
June 18, 2020

Valentin has seven years of experience in both startups and big French tech companies. He mainly worked as a back-end data engineer with Scala and Python. He is also familiar with working with Hadoop and Spark, developing data pipelines, and architecting data warehouses to extract value from terabytes of data. Valentin has recently been CTO for a YC tech startup leading a team of 10 to build complex front-end software as well as a full data processing engine in the back end.

Visual Studio Code (VS Code)ScalaPythonData PipelinesSQLPostgreSQLData EngineeringGitMySQLDockerRedisTypeScriptVueETLMicrosoft Excel

Portfolio

Actiondesk
Scala, Vue, Vuex, TypeScript, Apache Kafka, PostgreSQL, Google BigQuery...
Deezer
Apache Hive, HDFS, Hadoop, Apache Kafka, Spark, Scala, SQL, ETL, Data Pipelines...
Artefact
Apache Kafka, Storm, Hadoop, PostgreSQL, Spark, Scala, Django, Python, SQL, ETL...

Experience

Apache Kafka - 5 yearsScala - 5 yearsPython - 5 yearsSQL - 4 yearsHadoop - 3 yearsFunctional Programming - 3 yearsGoogle Cloud Platform (GCP) - 2 yearsAkka - 1 year

Availability

Part-time

Preferred Environment

Git, MacOS, Visual Studio Code (VS Code), Scala, Python, TypeScript, JavaScript, Vue, Google Cloud Platform (GCP)

The most amazing...

...project I've worked on is the refactoring of the most critical ETL of Deezer that calculates data used to compute recommendation, royalties, and analytics.

Work Experience

CTO

2019 - 2022
Actiondesk
  • Developed a spreadsheet application connected to dozens of integrations to make data engineering accessible to non-technical business users and automate their dashboards and reporting.
  • Conceived and led the implementation—first committer on every service for a long time—of the entire back end.
  • Managed a tech team of up to 10 engineers, including front-end, back-end, DevOps, and QA engineers.
  • Built dozens of connectors to databases and various APIs like Stripe, Hubspot, Google Analytics, and Quickbooks.
  • Created a formula engine to compute Excel-like formulas. The project was in ScalaJS to work both in the back end and in front end and have the exact same results.
  • Maintained a Kubernetes cluster for two years until I hired a DevOps engineer that I managed.
  • Implemented a sharing feature to share reports with charts on multiple channels, such as Slack, emails, etc.
Technologies: Scala, Vue, Vuex, TypeScript, Apache Kafka, PostgreSQL, Google BigQuery, WebSockets, Canvas, Redis, Kubernetes, SQL, Data Pipelines, Data Build Tool (dbt), Data Engineering, APIs, Microsoft Excel

Data Engineer

2017 - 2019
Deezer
  • Developed and maintained the core ETLs in Scala Spark and streaming pipelines with Kafka and Spark.
  • Streamed to process 2.5TB/day to support 50+ engineers, analysts, scientists, and product managers.
  • Managed data warehousing on HDFS in ORC, Parquet, and AVRO formats.
  • Developed our own scheduler in Python that runs 2,000 jobs per day.
Technologies: Apache Hive, HDFS, Hadoop, Apache Kafka, Spark, Scala, SQL, ETL, Data Pipelines, Data Engineering

Data Engineer

2016 - 2017
Artefact
  • Developed ETLs in PySpark in collaboration with data scientists.
  • Led as main contributor the internal data collection software processing 500GB per day.
  • Performed R&D for a stream processing project using Storm and Kafka.
Technologies: Apache Kafka, Storm, Hadoop, PostgreSQL, Spark, Scala, Django, Python, SQL, ETL, Data Pipelines, Data Engineering, APIs

Data Scientist

2015 - 2016
fifty-five
  • Optimized item ordering of product listings for major clothing retailers websites.
  • Developed user segmentation and buying prediction algorithms.
  • Optimized recommender systems parallelizing algorithms (ALS-WR) with CUDA.
Technologies: NVIDIA CUDA, C, BigQuery, Python, R, SQL

Back-end Engineer

2014 - 2015
Pricing Assistant
  • Developed an eCommerce page parser.
  • Developed product matchers in Python.
Technologies: Pandas, Flask, Python

Full Spreadsheet Application

https://actiondesk.io
A spreadsheet SAAS connected to 80+ databases and external tools.
As the CTO of Actiondesk, I created the architecture and was the lead developer to build the front-end application with Vue and a canvas rendering, as well as a complex data engine back end integrated with dozens of different DBs and external tools. I managed a team of up to 10 engineers, including front-end, DevOps, and all in between.

Facial Recognition

Wrote an entire facial recognition system. I reimplemented a math library based on standard library only and the computer vision algorithms (Eigenface and neural network). This was for a school project.

Migrated Critical Data Pipelines from Pig to Spark

Migrated the most critical data pipeline that made available the streams data (2.5+TB per day) ingested in daily batch to 60+ analysts and scientists for a leading music streaming company.
The migration saved more than 33% of computing time, making the data available before the analysts started their working day.
I worked on migrating the pipeline from Hive and Pig script to Spark with Scala, optimizing and simplifying the transformations.

Languages

SQL, Scala, Python, TypeScript, JavaScript, R, C, C++

Platforms

Visual Studio Code (VS Code), MacOS, Docker, Amazon Web Services (AWS), Google Cloud Platform (GCP), NVIDIA CUDA, Apache Pig, Apache Kafka, Kubernetes

Storage

PostgreSQL, Data Pipelines, Redis, Apache Hive, HDFS, MySQL, MongoDB

Other

APIs, Google BigQuery, Data Engineering, Distributed Systems, WebSockets, Data Build Tool (dbt)

Frameworks

Hadoop, Spark, Storm, Akka, Flask, Django

Libraries/APIs

Vue, Pandas, Vuex

Tools

Git, BigQuery, Microsoft Excel, IntelliJ IDEA, PyCharm, Ansible, Canvas

Paradigms

Functional Programming, ETL, Agile Software Development, Actor Model

2013 - 2016

Master's Degree in Computer Engineering

42 University - Paris, France