Josh Hamacher

Roughly half of my time has been allocated to company-wide technical leadership, tech debt cleanup, and proof-of-concept explorations. The remainder of my time has been spent embedded on different teams (roughly 3-6 months each) providing focused technical leadership and mentoring.

• Converted a heavy, bursty, high-traffic synchronous API endpoint into a simple enqueue-to-Sidekiq operation, reducing the number of active pods required to handle traffic by 50%.
• Added Redis caching for our most-used API endpoint, reducing load on our database and dropping the p50 for that endpoint from ~20ms to ~15ms.
• Simplified architecture by folding trivial microservice (low traffic, three API endpoints) back into our primary backend service (the only consumer).
• Removed unnecessary write-only sessions table from our main service, dropping p50 across all API calls from ~20ms to ~14ms.
• Led effort to enable YJIT in Ruby 3.2, resulting in about a 10% reduction in average API response time across the entire app.
• Designed and principally implemented a new data model and API to support a range of new product offerings.
• Key team member in the design and development of Cobalt's first public-facing API.

The Quartermaster team was responsible for self-service provisioning of internal MongoDB, MySQL, and Redis instances. As part of this team I made extensive changes to the core reservation logic, including the following:

• Introduced CPU oversubscription, allowing for better utilization of existing physical hosts and reducing the amount of hardware that needed to be purchased in each cycle.
• Introduced disk "reservable size", slightly smaller than physical size to protect against users filling up the disk and causing OS issues requiring physical intervention by the sysadmin team.
• Added ability to reserve multiple resources atomically, allowing for resources to be guaranteed to run on the same physical host(s).

The DREMR team was responsible for Indeed's external (jobseeker- and employer-facing) email infrastructure.

• Designed and implemented a MongoDB-backed caching layer to allow the replaying of email-creation requests from remote datacenters in the case of catastrophic link failure.
• Designed and implemented an abstraction layer/service for an LSM-tree-based on-disk data store, allowing us to begin breaking up and horizontally distributing a legacy monolithic program.

Amazon.com, Software Development Engineer II, 2008 January - 2014 December. I contributed to multiple internal tools teams, including helping to build Amazon's first internal Git-based revision control system.

FAAC Incorporated, Software Engineer 1-3, 1999 May - 2007 December. A small defense contractor in the simulation space, I participated in all aspects of creating and maintaining real-time QNX-hosted driver training simulators.