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Senior Machine Learning Engineer, Model Risk Management

Block, Inc. logo
Block, Inc.

Block, Inc. is a technology company building tools for economic empowerment, operating a portfolio of financial brands including Square, Cash App, Afterpay, TIDAL, Bitkey, and Proto. It serves sellers, consumers, artists, and bitcoin users through payments, banking, buy-now-pay-later, music streaming, and bitcoin self-custody and mining products.

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About Block, Inc.

Block, Inc. builds technology aimed at increasing access to the global economy. Its brands each unlock different aspects of the economy: Square makes commerce and financial services accessible to sellers; Cash App is an easy way to spend, send, and store money; Afterpay (Clearpay in the UK) helps customers manage spending over time; TIDAL is a music platform empowering artists as entrepreneurs; Bitkey is a self-custody bitcoin wallet; and Proto builds open, accessible bitcoin mining hardware and services. Block has been a long-time advocate for bitcoin, integrating bitcoin buying/selling and Lightning Network payments into Cash App and Square, funding open-source bitcoin infrastructure through Spiral (including the Lightning Development Kit), and engaging in bitcoin policy advocacy through groups like COPA, the Digital Energy Council, the Crypto Council for Innovation, and the Texas Blockchain Council. The company also runs a significant open source program (contributing to projects like Goose, an on-machine AI developer agent, OkHttp, Retrofit, gRPC, Envoy, and MySQL) and an AI research effort, including co-founding the Agentic AI Foundation with Anthropic and OpenAI. Block serves individual consumers, small and medium-sized businesses/merchants, artists, and developers.

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Skills

About the Role

You will independently challenge model owners across lending, fraud, and AML; reproduce their results, set and defend the acceptance thresholds, and own the call on whether a model is sound. Hunt the silent errors that make metrics lie, and prove them out before they reach production. Choose evaluation that holds up under real conditions: rare events, shifting populations, and drift that only shows up after launch. Work hands-on in codebases you did not write, learning the data, configs, and conventions, and ship production code in the tooling you build to validate them. Build the agentic validation tooling the team depends on, orchestrating agents that run in parallel. Reason about ML systems end to end — how features, training, serving, monitoring, and scale fit together — to evaluate and challenge an owner's design. Tie explainability and fair-lending findings on consumer credit models back to the model and product decisions that follow. Help define how Block validates the systems at the frontier of production AI, setting standards where none exist yet.

Requirements

  • A quantitative degree or equivalent experience, and senior-IC depth building or validating models in a high-stakes domain such as credit, fraud, or financial crime
  • Command of effective-challenge methodology reproduction conceptual-soundness review benchmarking stress testing and outcomes analysis with an eye for how a model holds up after launch and where its assumptions break
  • Deep applied ML and statistics across model families from regression and tree ensembles to deep learning with sound judgment about evaluation calibration and generalization
  • Experimentation and statistical rigor holdout and experiment design reasoning about uncertainty and evaluating a model beyond aggregate accuracy
  • Solid software and data engineering production-quality Python SQL on large datasets and reproducible tested code
  • Fluency with modern AI building with LLMs and agentic tools and the judgment to know when their output can be trusted
  • Familiarity with model risk management frameworks and fair-lending standards with the specifics learnable on the job
  • The communication to explain and defend your conclusions to model owners and senior stakeholders and the independence to operate under ambiguity

Responsibilities

  • Independently challenge model owners across lending, fraud, and AML; reproduce results, set acceptance thresholds, and own the call on whether a model is sound
  • Hunt silent errors that mislead metrics and prove them out before production
  • Choose evaluation that holds up under real conditions rare events shifting populations and drift that only shows up after launch
  • Work hands-on in codebases you did not write learning the data configs and conventions and ship production code in the tooling you build to validate them
  • Build the agentic validation tooling the team depends on orchestrating agents that run in parallel
  • Reason about ML systems end to end how features training serving monitoring and scale fit together to evaluate and challenge an owner's design
  • Tie explainability and fair lending findings on consumer credit models back to the model and product decisions that follow
  • Help define how Block validates the systems at the frontier of production AI setting standards where none exist yet

Benefits

  • Remote work
  • medical insurance
  • flexible time off
  • retirement savings plans
  • modern family planning