Nicholas Hoffmann

Engineering Leader for the Data Platform • Senior leader for 5 teams and over 50 engineers. Managing team engineering managers and area technical leads. My teams process and store petabytes of data on AWS using Kafka, Spark, Iceberg, Clickhouse, MySQL Aurora, DataHub, and other technologies. • Created project management, engineering operations, and hiring best practices that were adopted as the standard by my SVP's entire organization and used across engineering. • Organized my teams to regularly release powerful platform capabilities that enabled Engineering, Data Science, and Business Intelligence at Klaviyo including AI/ML training productivity enhancements, data governance and compliance, data cataloging and lineage tracking, and flexible query capabilities across our analytical data systems. • Helped my teams to release highly impactful customer facing features including segment preview, faster campaign recipient calculation, and cohort reporting on schedule and with high operational stability. • Worked with my teams and others across engineering to ensure that Klaviyo had our biggest and most successful Black Friday and Cyber Monday ever in 2025

Engineering Manager and Technical Lead • Managed fourteen engineers on two teams, providing coaching and focused growth opportunities to help each team member meet their career goals and the teams as a whole accomplish their objectives. Hired other engineering managers to support the creation of distinct sub-teams to support better focus and improved growth opportunities. • Led an ambitious project to rebuild the Klaviyo segmentation engine using ClickHouse and Kafka that led to dramatically reduced infrastructure and operational costs while laying the groundwork for new segmentation functionality. • Designed and implemented improvements to the segmentation pipeline to make it more robust in the face of upstream and downstream failures and enabling automatic recovery while also improving throughput per processing host by 5x. • Worked with our Product, Customer Success, and Business Analytics teams to identify high impact work to improve the customer experience and reduce chat and email support volume. Planned and shipped changes that reduced support requests for the team's product areas by 45%. • Guided the team through creation of Klaviyo's new Custom Analytics reporting tool and made sure the project was completed on time with the desired functionality. • Designed, led, and helped implement an engineering wide effort to migrate to a new primary key identifier for profile database tables which involved migrating tens of thousands of sharded and non-sharded MySQL tables. • Guided the team through large refactors of our profiles and subscription management functionality which reduced a large number of bugs, improved maintainability, gave our customers a more cohesive and consistent experience, and opened the doors to further feature improvements.

Engineering Lead for Reporting, Segmentation, and Profiles. • Scaled my team's systems to handle 3x our prior peak load over Black Friday and Cyber Monday 2019. • Set up ProxySQL to manage connections for several frequently accessed databases. • Created a sharded database re-balancing toolkit and process. Used those tools and processes to scale and re-balance databases with tables that collectively contained billions of rows. • Worked with my team to design and implement a reporting engine that connected all of the data stores in Klaviyo using Apache Flink. Created a PostgreSQL database to track report definitions and versions, built out APIs to allow report creation through the Klaviyo app UI, and created a custom Java StatsD client to allow for monitoring of the reporting engine with our existing Graphite/Grafana infrastructure. • Tuned MySQL database tables and queries against those tables to reduce CPU load by 5x, allowing my team to use smaller and cheaper AWS instance types while also reducing data latency. • Created an integration between Sentry and TargetProcess to help my team easily track work related to fixing errors generated in our product areas. Used this process to fix all unhandled exceptions in our code which reduced alert fatigue and increased app stability and visibility into new issues. • Prepared the product for Black Friday / Cyber Monday by scaling for 5x load, including optimizing data access patterns, sharding and upsizing MySQL databases, and adding sharded caching with Redis and memcached for high volume reads.

Engineering Lead for Reporting, Segmentation, and Profiles. • Designed and implemented location based segmentation. • Analyzed the real-time segment processing pipeline and identified a potential 65% reduction in processing load and AWS cost. Planned, designed, and implemented a solution to realize that savings. • Designed and implemented new APIs for third-party integration with Klaviyo. • Planned and implemented GDPR compliance changes for customer profile management. • Optimized code paths for efficient data access from a combination of MySQL and Cassandra data stores. • Redesigned and refactored Klaviyo's segmentation functionality to provide over 30x speed improvement and cost savings of 84%. • Created automated regression testing suite to allow changes to be made to the segmentation code with speed and confidence. • Created generalized automated task reprocessing and status reporting using ElasticSearch and Kibana.

Software Engineer for cloud based healthcare IT systems. Software Engineer and Scrum Master on the Authorization Management Team • Developed cloud based software solutions for primary care physicians and specialist providers to improve patient access to medical care. • Lead the team in Agile Best Practices and contributed to the technical success of the project. Software Engineer on the Remittance and Processing Operations Team • Analyzed insurance payer payment data to automate refund generation and reduce client friction. • Added new patient payment tracking functionality to improve billing transparency. • Developed a corporate billing and payment posting system to allow corporate clients to use athenahealth’s credit card payment portal. • Coordinated between a business team based in the US and a development team based in India as the stateside technical lead, including travel to Chennai, Tamil Nadu, India.

Software and systems engineer for high-resolution visual and infrared satellite imagery processing systems. • Designed, implemented, and tested a Java-based RESTful web services architecture for a new remote ground system to downlink and process commercial satellite imagery. Demonstrated project on-site in Washington, D.C. and Okinawa, Japan. • Designed, implemented, and tested new product updates including new image sharpening algorithms, improved image color balancing, and performance improvements. • Defined requirements, concept of operations, and necessary updates to system ICDs and APIs as part of the Systems Engineering Team and as Integration and Test Lead for the WorldView-3 upgrade for DigitalGlobe. • Provided post-launch support for WorldView-3 to DigitalGlobe’s radiometric and geometric calibration groups to characterize the satellite after launch. • Developed a full end-to-end test suite for the core software product using Python with parallel processing which reduced integration testing time by 65%.

Colorado Center for Astrodynamics Research (CCAR) Created software solutions to synthesize and analyze a variety of satellite data sources for physical oceanography applications. • Created and applied a Gulf of Mexico current tracking and statistical analysis toolbox. • Created Empirical Orthogonal Functions (EOFs) program to identify dominant patterns in the Gulf of Mexico Loop Current eddy separation cycle. • Created and applied a 3-D interpolation and particle path integration program to identify Lagrangian Coherent Structures. Used this program to simulate and analyze the Deepwater Horizon oil spill. • Synthesized thermal and visual data sets to identify cold core eddies off the coast of Hawaii. • Worked with data from the NOAA-AVHRR, MODIS-Aqua, Topex/Poseidon, Jason-1, and OSTM/Jason-2 missions.