Principal Engineer, AI Systems

$319K - $478K San Francisco Bay Area, CA, US Senior AI/ML Engineer

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Skills & Technologies

Prompt EngineeringRlhf

About This Role

AI job market dashboard showing open roles by category

Block builds simple, powerful tools that make progress towards an economy that's truly open to all.

Each of our brands unlocks different aspects of the economy for more people. Square makes commerce and financial services accessible to sellers. Cash App is the easy way to spend, send, and store money. Afterpay is transforming the way customers manage their spending over time. TIDAL is a music platform that empowers artists to thrive as entrepreneurs. Bitkey is a simple self\-custody wallet built for bitcoin. Proto is a suite of bitcoin mining products and services. Together, we're helping build a financial system that is open to everyone. Join us.

#### The Role

Block is building toward one of the most ambitious technical visions in our history: an AGI\-enabled entity that fundamentally transforms how we deliver economic empowerment. We're assembling a world\-class team of AI experts to design and ship autonomous agents and agentic workflows that operate across Square, Cash App, and the broader Block ecosystem. This work is about creating solutions—you'll be building AI that acts, decides, and completes real tasks for real users from across all of Block's business functions. As a Principal Engineer, you'll join as a senior individual contributor with significant technical leadership responsibilities.

#### You Will

  • Ship, architect, build, and own end\-to\-end delivery of autonomous agents and agentic workflows that deliver real business value for Block, ensuring reliability, safety, and performance at scale
  • Design agent orchestration systems including planning, tool use, memory, evaluation, and multi\-agent coordination at production scale
  • Integrate and optimize frontier LLMs into agent architectures, making decisions on model selection, fine\-tuning, prompt engineering, and context retrieval strategies
  • Drive deeper model optimization work (fine\-tuning, distillation, RLHF) where it unlocks agent capability or efficiency
  • Lead detailed technical planning by breaking down ambitious objectives into concrete, sequenced tasks with clear ownership and execution paths
  • Provide technical mentorship and guidance to engineers across experience levels, elevating team capabilities through code review, pairing, and knowledge sharing
  • Partner closely with technical and non\-technical stakeholders to translate business objectives into agent\-powered product experiences
  • Keep Block at the frontier by continuously evaluating emerging AI capabilities and making pragmatic tradeoffs across model performance, latency, cost, and user experience
  • Foster a culture of technical excellence, high\-quality delivery, rapid experimentation, and learning within your team and beyond

#### You Have

  • 15\+ years of experience in software engineering or machine learning, with recent professional experience building autonomous agents or agentic workflows in production
  • Deep experience building autonomous agents or agentic workflows in production environments—not just prototypes or demos
  • Fluency in the core primitives of agentic systems: context management, planning, tool use, memory, evaluation, and multi\-step reasoning
  • Experience bringing frontier LLM capabilities into production products, with hands\-on experience in prompt engineering, retrieval\-augmented generation, and model optimization
  • A track record of taking AI\-powered products from zero to scale in fast\-paced, product\-driven environments, with the judgment that comes from operating in production
  • Strong software engineering fundamentals with the ability to write production\-quality code and make sound architectural decisions
  • Experience providing technical leadership within teams—you've shaped technical direction, driven execution, and elevated others
  • Product\-minded engineering approach—you think in terms of user outcomes, not just model metrics
  • Excellent collaboration and communication skills, with ability to build alignment across engineering, product, and design
  • Comfort navigating extreme ambiguity in a domain that's evolving weekly
  • Alignment with Block's mission of economic empowerment and using technology to create access and opportunity

#### Bonus Points For

  • Experience at leading AI organizations with a track record of translating research into production agent systems
  • Background building or scaling agentic products at startups (including early\-stage or pivoting companies)
  • Experience with model fine\-tuning, distillation, or RLHF to improve agent performance
  • Familiarity with agent evaluation, safety, and alignment challenges in production contexts

We’re working to build a more inclusive economy where our customers have equal access to opportunity, and we strive to live by these same values in building our workplace. Block is an equal opportunity employer evaluating all employees and job applicants without regard to identity or any legally protected class. We will consider qualified applicants with arrest or conviction records for employment in accordance with state and local laws and “fair chance” ordinances.

We believe in being fair, and are committed to an inclusive interview experience, including providing reasonable accommodations to disabled applicants throughout the recruitment process. We encourage applicants to share any needed accommodations with their recruiter, who will treat these requests as confidentially as possible.

While there is no specific deadline to apply for this role, U.S. roles are typically open for an average of 55 days before being filled by a successful candidate. Please refer to the date listed at the top of this job page for when this role was first posted.

Block takes a market\-based approach to pay, and pay may vary depending on your location. U.S. locations are categorized into one of four zones based on a cost of labor index for that geographic area. The successful candidate’s starting pay will be determined based on job\-related skills, experience, qualifications, work location, and market conditions. These ranges may be modified in the future.

Zone A:

$319,000—$478,600 USD

Zone B:

$319,000—$478,600 USD

Zone C:

$319,000—$478,600 USD

Zone D:

$319,000—$478,600 USDApplication Guidelines

Candidates may submit up to 9 active applications within a 60\-day period. Reapplications to the same role are accepted 90 days after a previous application has been reviewed.

Use of AI in Our Hiring Process

We may use automated AI tools to evaluate job applications for efficiency and consistency. These tools comply with local regulations, including bias audits, and we handle all personal data in accordance with state and local privacy laws.

Contact us here with hiring practice or data usage questions.

*Every benefit we offer is designed with one goal: empowering you to do the best work of your career while building the life you want. Remote work, medical insurance, flexible time off, retirement savings plans, and modern family planning are just some of our offering.*

*Block, Inc. (NYSE: XYZ) builds technology to increase access to the global economy. Each of our brands unlocks different aspects of the economy for more people.* *Square* *makes commerce and financial services accessible to sellers.* *Cash App* *is the easy way to spend, send, and store money.* *Afterpay* *is transforming the way customers manage their spending over time.* *TIDAL* *is a music platform that empowers artists to thrive as entrepreneurs.* *Bitkey* *is a simple self\-custody wallet built for bitcoin.* *Proto* *is a suite of bitcoin mining products and services. Together, we’re helping build a financial system that is open to everyone.*

Salary Context

This $319K-$478K range is above the 75th percentile for AI/ML Engineer roles in our dataset (median: $180K across 2130 roles with salary data).

View full AI/ML Engineer salary data →

Role Details

Company Block
Title Principal Engineer, AI Systems
Location San Francisco Bay Area, CA, US
Category AI/ML Engineer
Experience Senior
Salary $319K - $478K
Remote No

About This Role

AI/ML Engineers build and deploy machine learning models in production. They work across the full ML lifecycle: data pipelines, model training, evaluation, and serving infrastructure. The role has evolved significantly over the past two years. Where ML Engineers once spent most of their time on model architecture, the job now tilts heavily toward inference optimization, cost management, and integrating LLM capabilities into existing systems. Companies want engineers who can ship production systems, and the experimenter-only role is fading fast.

Day-to-day, you're writing training pipelines, debugging data quality issues, setting up evaluation frameworks, and figuring out why your model performs differently in staging than it did on your dev set. The best ML engineers are obsessive about reproducibility and measurement. They instrument everything. They know that a model is only as good as the data feeding it and the infrastructure serving it.

Across the 4,133 AI roles we're tracking, AI/ML Engineer positions make up 69% of the market. At Block, this role fits into their broader AI and engineering organization.

Demand for AI/ML Engineers has been strong and consistent. Unlike some AI roles that spike with hype cycles, ML engineering is a foundational need. Every company deploying AI models needs people who can keep them running, and the gap between research prototypes and production systems keeps growing.

What the Work Looks Like

A typical week might include: debugging a data pipeline that's silently dropping 3% of training examples, running A/B tests on a new model version, writing documentation for a feature flag system that lets you roll back model deployments, and reviewing a junior engineer's PR for a new evaluation metric. Meetings tend to be cross-functional since ML touches product, engineering, and data teams.

Demand for AI/ML Engineers has been strong and consistent. Unlike some AI roles that spike with hype cycles, ML engineering is a foundational need. Every company deploying AI models needs people who can keep them running, and the gap between research prototypes and production systems keeps growing.

Skills Required

Prompt Engineering (15% of roles) Rlhf (1% of roles)

Python and PyTorch dominate the requirements. Most roles expect experience with cloud platforms (AWS, GCP, or Azure) and familiarity with ML frameworks like TensorFlow or JAX. RAG (Retrieval-Augmented Generation) has become a top-3 skill requirement as companies integrate LLMs into their products. Docker and Kubernetes show up in about a third of postings, reflecting the production focus of the role.

Beyond the core stack, employers increasingly want experience with experiment tracking tools (MLflow, Weights & Biases), feature stores, and vector databases. Fine-tuning experience is valuable but less common than you'd think from reading Twitter. Most production LLM work is RAG and prompt engineering, not fine-tuning. If you have both, you're in a strong position.

Companies that are serious about AI/ML hiring tend to post specific infrastructure details in the job description: the frameworks they use, their model serving stack, their data pipeline tools. Vague postings that just say 'ML experience required' without specifics are often companies that haven't figured out what they need yet.

Compensation Benchmarks

AI/ML Engineer roles pay a median of $185,000 based on 13,200 positions with disclosed compensation. Senior-level AI roles across all categories have a median of $227,400. This role's midpoint ($398K) sits 116% above the category median. Disclosed range: $319K to $478K.

Across all AI roles, the market median is $200,700. Top-quartile compensation starts at $254,000. The 90th percentile reaches $307,500. For comparison, the highest-paying categories include AI Safety ($274,200) and AI Engineering Manager ($268,700). By seniority level: Entry: $97,760; Mid: $165,778; Senior: $227,400; Director: $250,000; VP: $250,000.

Block AI Hiring

Block has 5 open AI roles right now. They're hiring across AI/ML Engineer. Positions span San Francisco Bay Area, CA, US, Seattle, WA, US, New York, NY, US. Compensation range: $343K - $478K.

Location Context

AI roles in San Francisco pay a median of $253,000 across 2,258 tracked positions. That's 26% above the national median.

Career Path

Common paths into AI/ML Engineer roles include Data Scientist, Software Engineer, Research Engineer.

From here, career progression typically leads toward ML Architect, AI Engineering Manager, Principal ML Engineer.

The fastest path into ML engineering is through software engineering with a self-directed ML education. A CS degree helps, but production engineering skills matter more than academic credentials. Build something that works, deploy it, and measure it. That portfolio project is worth more than a Coursera certificate. For career growth, the fork comes around the senior level: go deep on technical complexity (staff/principal track) or move into managing ML teams.

What to Expect in Interviews

Expect system design questions around ML pipelines: how you'd build a training pipeline for a specific use case, handle data drift, or design A/B testing infrastructure for model deployments. Coding rounds typically involve Python, with emphasis on data manipulation (pandas, numpy) and algorithm implementation. Take-home assignments often ask you to build an end-to-end ML pipeline from raw data to deployed model.

When evaluating opportunities: Companies that are serious about AI/ML hiring tend to post specific infrastructure details in the job description: the frameworks they use, their model serving stack, their data pipeline tools. Vague postings that just say 'ML experience required' without specifics are often companies that haven't figured out what they need yet.

AI Hiring Overview

The AI job market has 4,133 open positions tracked in our dataset. By seniority: 106 entry-level, 1,901 mid-level, 1,663 senior, and 463 leadership roles (Director, VP, C-Level). Remote roles make up 14% of the market (583 positions). The remaining 3,532 roles require on-site or hybrid attendance.

The market median for AI roles is $200,700. Top-quartile compensation starts at $254,000. The 90th percentile reaches $307,500. Highest-paying categories: AI Safety ($274,200 median, 57 roles); AI Engineering Manager ($268,700 median, 42 roles); Research Engineer ($260,000 median, 442 roles).

Demand for AI/ML Engineers has been strong and consistent. Unlike some AI roles that spike with hype cycles, ML engineering is a foundational need. Every company deploying AI models needs people who can keep them running, and the gap between research prototypes and production systems keeps growing.

The AI Job Market Today

The AI job market spans 4,133 open positions across 15 role categories. The largest categories by volume: AI/ML Engineer (2,865), Data Scientist (339), AI Software Engineer (313). These three account for the majority of open positions, though smaller categories often have higher per-role compensation because of specialized skill requirements.

The seniority mix tells a story about where AI teams are in their maturity. Entry-level roles (106) are outnumbered by mid-level (1,901) and senior (1,663) positions, reflecting that most companies are past the 'build a team from scratch' phase and need experienced engineers who can ship production systems. Leadership roles (Director, VP, C-Level) total 463 positions, representing the bottleneck between technical execution and organizational strategy.

Remote work availability sits at 14% of all AI roles (583 positions), with 3,532 requiring on-site or hybrid attendance. The remote share has stabilized after the post-pandemic correction. Senior and specialized roles (Research Scientist, ML Architect) are more likely to be remote-eligible than entry-level positions, partly because experienced hires have more negotiating power and partly because these roles require less hands-on mentorship.

AI compensation is structured in clear tiers. The market median sits at $200,700. Top-quartile roles start at $254,000, and the 90th percentile reaches $307,500. These figures include base salary with disclosed compensation. Total compensation (including equity, bonuses, and sign-on) runs 20-40% higher at companies that offer those components.

Category matters for compensation. AI Safety roles lead at $274,200 median, while Prompt Engineer roles sit at $140,000. The spread between highest and lowest-paying categories reflects the premium on specialized technical skills versus broader analytical roles.

The most in-demand skills across all AI postings: Python (2,128 postings), Aws (1,324 postings), Azure (1,003 postings), Rag (916 postings), Gcp (817 postings), Pytorch (655 postings), Prompt Engineering (639 postings), Claude (571 postings). Python dominates, appearing in the vast majority of role descriptions regardless of category. Cloud platform experience (AWS, GCP, Azure) is the second most common requirement. The newer entrants to the top skills list (RAG, vector databases, LLM APIs) reflect the shift from traditional ML toward generative AI applications.

Frequently Asked Questions

Based on 13,200 roles with disclosed compensation, the median salary for AI/ML Engineer positions is $185,000. Actual compensation varies by seniority, location, and company stage.
Python and PyTorch dominate the requirements. Most roles expect experience with cloud platforms (AWS, GCP, or Azure) and familiarity with ML frameworks like TensorFlow or JAX. RAG (Retrieval-Augmented Generation) has become a top-3 skill requirement as companies integrate LLMs into their products. Docker and Kubernetes show up in about a third of postings, reflecting the production focus of the role.
About 14% of the 4,133 AI roles we track offer remote work. Remote availability varies by company and seniority level, with senior and leadership roles more likely to offer location flexibility.
Block is among the companies actively hiring for AI and ML talent. Check our company profiles for detailed breakdowns of open roles, salary ranges, and hiring trends.
Common next steps from AI/ML Engineer positions include ML Architect, AI Engineering Manager, Principal ML Engineer. Progression depends on whether you lean toward technical depth, people management, or product strategy.

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