Vitthal Mirji

Summary

Staff Software Engineer with 12+ years building internal developer platforms, type-safe SDK libraries, and data infrastructure at Walmart-scale and Deloitte Fortune 500 clients. Authored compile-time schema contract systems adopted across 40+ teams and 150+ engineers. Designed and shipped six reusable frameworks - contracts, archetypes, monitoring, quality, and operations - that other engineers depend on daily.

Led architecture for platforms processing 100M+ daily records on Spark/Databricks and Kafka/Flink, with sub-2h data freshness. Mentored 8 senior engineers on functional Scala, ADRs, and staff-level readiness. Translated product bets into architecture and adoption roadmaps across cross-functional teams.

Builds things other engineers depend on - and shows up the same way every time. Creator of flowforge and toon4s, core contributor to llm4s, cask, and scalasql. International speaker (Scala.io Paris, Data Makers Fest, Lambda Days, GDG, JUGs, OAISYS). Bootcamp instructor for Fortune 500 teams.

Key Accomplishments

• Designed internal developer platform adopted by 150+ engineers across 40+ teams - six type-safe SDK libraries (contracts, archetypes, monitoring, quality, operations) that cut delivery from six weeks to two and reduced incidents by ~82%.
• Engineered closed-loop merchant analytics platform processing 100M+ daily records on Spark/Databricks, unlocking 75% business growth with sub-2h data freshness.
• Modernized Deloitte Fortune 500 estates (Aflac, Marriott, Eli Lilly), trimming infra spend by 62% (US$2.4M→US$900K) and boosting SLAs to 99.5%.
• Built observability platform (DPAT automation + data-quality engines) validating 5TB+/day at 99.9% accuracy, reducing MTTR by 60% and shrinking QA sign-off from three days to four hours.
• Authored flowforge and toon4s; core contributor to llm4s (GSoC mentor), cask, and scalasql. International speaker at Scala.io Paris, Data Makers Fest, OAISYS, GDGs. Bootcamp instructor for Fortune 500 engineering teams.

Core Skills

Architecture: API design, SDK authorship, system design, data contracts, streaming observability, data governance, platform engineering, data warehousing, data modeling.

Expert: Scala (Typelevel, Cats Effect, meta-programming), Python, SQL, Java.

Productive / Actively Growing: Kotlin, Rust, Bash.

Foundational: C++.

Engines & Cloud: Spark, Databricks, Flink, Kafka, Beam · GCP (BigQuery, Dataproc, GCS, Pub/Sub), AWS (S3, Glue, EMR) · Docker, Kubernetes.

Leadership: Staff+ design reviews, roadmap definition, cross-team adoption playbooks, senior IC mentoring (8 engineers), incident/SLO programs, product-to-architecture translation.

Work

Open Source

Author and core contributor to Scala libraries spanning platform engineering, compile-time safety, LLM infrastructure, and upstream ecosystem contributions.

• cask (github.com/com-lihaoyi/cask): Added DB transaction support and application configuration handling to Li Haoyi's Scala web framework.
• scalasql (github.com/com-lihaoyi/scalasql): Added COUNT and COUNT(DISTINCT) aggregation support to Li Haoyi's type-safe SQL library.
• flowforge (github.com/vim89/flowforge): Type-safe Scala data-engineering SDK with compile-time contract validation. Prevents schema drift before deploy.
• toon4s (github.com/com-vitthalmirji/toon4s): Token-Oriented Object Notation for JVM. Reduces LLM token costs by 30–60% while maintaining JSON compatibility. 500+ tests, JMH benchmarks, Maven Central.
• llm4s (github.com/llm4s/llm4s): Core contributor and GSoC mentor. Type-safe LLM framework for Scala with multi-provider support, agents, RAG, and tracing.
• compile-time-data-contracts (github.com/vim89/compile-time-data-contracts): Scala 3 macro-based schema validation. Pipelines fail to compile on schema drift.
• datapipelines-essentials-python (github.com/vim89/datapipelines-essentials-python): Reusable Spark ETL library with SparkSession extensions, DataFrame validation, and SQL functions.
• abortable-bytes (github.com/vim89/abortable-bytes): Kyo effect-system POC for cancel-safe cloud uploads with automatic cleanup.
• spark-xml: Contributor to Databricks' Spark XML library.
• Rock the JVM (rockthejvm.com): Author of Scala technical articles.

Publications

• Shift schema drift left: Policy-aware compile-time contracts for typed JVM and Apache Spark pipelines. arXiv:2604.16986

Talks / Speaking

• Scala.io Paris, France October 2025: Compile-time data contracts & Fiber-safe Data pipelines: Scala’s Effect system in action
• OAISYS - 2025 AI PRACTITIONERS CONFERENCE, Pune India November 2025: LLM4S: Build Reliable AI Systems in the JVM Ecosystem
• Scala India, September 2025: When Data pipelines fail early: Type-safe Data Engineering in Scala
• DroidFest 2026 by Kotlin Kolkata: Type Classes in Kotlin - Without the Magic.
• Lambda days J on the Beach, Spain: Hands-on workshop: Rust ate Spark's lunch: DataFusion pipelines without the JVM.
• Data Makers Fest International Conference 2026: Organising team & volunteer. May 4–6, 2026.
• GDG & JUGs: Regular speaker at Google Developer Groups, Google Developer Expert and Java/Kotlin User Group meetups on Scala, Spark, and Data Architecture.
• Bootcamps: Run internal training on data engineering, functional programming for Fortune 500 teams.

Publish 25K+ view technical articles on vitthalmirji.com covering type-safe data engineering, Scala patterns, and production lessons.

Education

• B.E. Computer Science - Visvesvaraya Technological University, First Class, Jun 2015 (Belgaum, India).
• Diploma Computer Science - Bangalore University, First Class Distinction, 2010.

Certifications

• Google Professional Data Engineer - Feb 2021.
• Cloudera Certified Spark & Hadoop Developer - May 2020.
• Sun Certified Java Developer - Java 5.x (2009), 6.x (2010).

Recognition

• Walmart Bravo Award - 2024 & 2021.
• Walmart Wall of Fame - 2021-2024.
• Deloitte Outstanding Performance - 2019.
• Multiple Deloitte Applause Awards - 2017-2021.
• Best Academic Project (1st/15) - 2015, Gogte Institute of Technology.