Senior Software Engineer, Backend (Cost Engineering)

Affirm, Inc.; United States; Remote; USD 108,000 - 151,000; Full time

Benefits offered by this job

Health coverage

Tech stipends

Flexible time off

Employee stock purchase plan

Job summary

Affirm, Inc. is seeking a Capacity Modeling Engineer to own quarterly goals for a high-scale backend team. You will lead engineers through ambiguity and ensure delivery while partnering with product, design and analytics to navigate constraints and risks.

You will build statistical capacity models mapping demand to resources (CPU, memory, connections) and translate forecasts into concrete capacity settings across regions and environments, balancing reliability with cost.

Qualifications

• 4+ years designing, developing and launching backend systems at scale.
• Proven distributed systems experience using AWS, MySQL and Kubernetes.
• Experience supporting scale during large sales events (e.g., Prime Day, Black Friday).

Responsibilities

• Own and deliver quarterly goals for the capacity team and lead engineers through ambiguity.
• Collaborate with product, design and analytics to balance constraints and risks.
• Identify and drive resolution of project, process or tech issues.
• Support operations and on-call efforts to keep artifacts available.
• Set and improve code review and design standards beyond the team.
• Mentor and develop team members with feedback and guidance.

Skills

Backend design

Distributed systems

Cloud computing

Code quality

Education

Bachelor’s degree or equivalent

Tools

AWS

Kubernetes

MySQL

Python

Kotlin

Job description

At the company, we exist for the moments that matter—giving people a clear, predictable way to pay over time, with no hidden fees, no surprises, and no tradeoffs on what matters most.

The Capacity Modeling team ensures the company can safely handle forecasted traffic—especially during peak sales events—by translating demand forecasts into concrete, testable capacity plans. They build and maintain statistical capacity models that map traffic inputs (e.g., checkout volume, app opens, batch/job activity) to resource outputs (CPU, memory, connections) and then convert those forecasts into recommended capacity settings such as pod counts, HPA ranges, and/or infrastructure sizing changes across regions and environments.

What You'll Do

• You will be responsible for owning and delivering quarterly goals for your team, leading engineers on your team through ambiguity to solve open-ended problems, and ensuring that everyone is supported throughout delivery.
• You will support your peers and stakeholders in the product development lifecycle by collaborating with product management, design & analytics by participating in ideation, articulating technical constraints, and partnering on decisions that properly consider risks and trade-offs.
• You will proactively identify project, process, technology or business issues, advocate for them, and lead in solving them.
• You will support the operations and availability of your team’s artifacts by creating and monitoring metrics, escalating when needed, and supporting “keep the lights on” & on-call efforts.
• You will foster a culture of quality and ownership on your team by setting or improving code review and design standards for your team, and advocating for them beyond your team through your writing and tech talks.
• You will help develop talent on your team by providing feedback and guidance, and leading by example.

What We Look For

• You have 4+ years of experience designing, developing and launching backend systems at scale using languages like Python or Kotlin.
• You have a track record of developing highly available distributed systems using technologies like AWS, MySQL and Kubernetes.
• You have experience supporting scale up and down of large scale sales event such as Prime Day, Black Friday Cyber Monday, or other sales holidays

• You have tuned autoscaling, CPU/Memory, and multi-threading for compute type workloads.
• You have experience defining a technical plan for the delivery of a significant feature or system component with an elegant, simple and extensible design. You write high quality code that is easily understood and used by others.
• You are proficient at making significant changes in a large code base, and have developed a suite of tools and practices that enable you and your team to do so safely.
• Your experience demonstrates that you take ownership of your growth, proactively seeking feedback from your team, your manager, and your stakeholders.
• You have strong verbal and written communication skills that support effective collaboration with our global engineering team.
• This position requires either equivalent practical experience or a Bachelor’s degree in a related field.

Pay Grade - NEquity Grade - 6

Employees new to the company typically come in at the start of the pay range. the company focuses on providing a simple and transparent pay structure which is based on a variety of factors, including location, experience and job-related skills.

Base pay is part of a total compensation package that may include monthly stipends for health, wellness and tech spending, and benefits (including 100% subsidized medical coverage, dental and vision for you and your dependents). In addition, the employees may be eligible for equity rewards offered by the company Holdings, Inc. (parent company).

CAN base pay range per year: CAD $153,000 - $213,000.

Location - Remote Canada

This remote role is open only to candidates residing in Alberta, British Columbia, Manitoba, New Brunswick, Newfoundland and Labrador, Nova Scotia, Ontario, Prince Edward Island, or Saskatchewan.

This posting is for an existing vacancy.

#LI Remote

Remote-first with flexibility built in

the company is proud to be a remote-first company. Most roles can be done from almost anywhere within the country of employment. Some positions may occasionally require in-person work at an the company office, and a few are office-based due to the nature of the work. All new hires will be invited to attend an in-person onboarding experience.

Benefits designed for you

Our benefits reflect our commitment to care, transparency, and flexibility. Here are a few highlights:

• Health coverage at no cost: We cover 100% of premiums for employees and their dependents.

• Spending stipends: Monthly stipents support your tech setup, and the ability to choose health and wellness options that are right for you.

• Time off to recharge: Flexible time off and generous holiday calendars help you rest when you need to.

• Own a piece of what you build: Our employee stock purchase plan (ESPP) lets you buy the company stock at a discount.

We’re committed to providing an inclusive interview process, including accommodations for candidates with disabilities. If you need support, we’re happy to help.

For positions based in San Francisco or Los Angeles: the company considers qualified applicants with arrest and conviction records, as required by law.