Senior Software Engineer, Backend (Cost Engineering)

Affirm, Inc.; Ottawa; Remote; CAD 153,000 - 213,000; Full time

Benefits offered by this job

Health coverage for you and dependents

Monthly tech stipends

Generous time off

Employee stock purchase plan (ESPP)

Job summary

Affirm, Inc. is seeking an experienced Capacity Modeling Engineer to own quarterly goals and lead engineers through ambiguity. You will work with product, design and analytics to align on constraints and trade-offs, while driving reliable capacity plans across regions.

You will design and maintain capacity models, tune autoscaling, and ensure high availability during peak events. This role requires ownership mindset and strong cross-team communication.

Qualifications

• 4+ years designing, developing and launching backend systems at scale.
• Proven experience with highly available distributed systems (AWS, MySQL, Kubernetes).
• Experience supporting scale up/down for major sales events.
• Tuning autoscaling, CPU/memory and multi-threading for compute workloads.
• Ability to define technical plans for major features with simple, extensible design.
• Write high-quality code that is understandable and usable by others.
• Ability to make safe, large codebase changes with tooling and practices.
• Strong communication for collaboration with a global team.

Responsibilities

• Own and deliver quarterly goals for your team, guiding engineers through ambiguity.
• Collaborate with product management, design & analytics in ideation and decisions.
• Identify issues proactively and lead in solving them.
• Support operations and on-call efforts; monitor metrics and escalate when needed.
• Set or improve code review and design standards beyond your team.
• Develop talent by providing feedback and guidance.

Skills

Python

Kotlin

Leadership

Communication

Education

Bachelor's degree or equivalent

Tools

AWS

MySQL

Kubernetes

Job description

At Aff, 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 Aff**irm 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 - N

Equity Grade - 6

Employees new to Aff typically come in at the start of the pay range. Aff 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 Aff 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.

Remote

Remote-first with flexibility built in

Affirm 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 Aff 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 stipends 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 Aff 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: Affirms considers qualified applicants with arrest and conviction records, as required by law.