Staff Backend Engineer - Payments Platform & APIs

Flex; San Francisco (CA); Hybrid; USD 200,000 - 250,000; Full time

Benefits offered by this job

Competitive benefits

Company equity

401(k) with match

Unlimited PTO + holidays

Parental leave

Relocation assistance

Job summary

Flex is a growth-stage FinTech with NYC roots and teams across the US.

As a Staff Backend Engineer, you will design, build, and scale the services behind Payment, Billing, Identity, and partner integrations, setting the long-term technical vision and architecture for the systems you own, leading scoping, design, and implementation across teams, driving your own production rollouts to completion with minimal oversight, and working closely with product, design, and engineering peers to solve

Qualifications

• 8+ years in software engineering.
• 6+ years with Java.
• Set technical direction and architecture for distributed systems.
• Lead and mentor engineers across teams.
• Work on a globally distributed team with ownership.
• Experience aligning scope and delivery with stakeholders.
• Build robust, fault-tolerant systems with external dependencies.
• Design, build, and maintain data pipelines.
• Proficient in Java frameworks: Spring, Gradle, JUnit; JVM tuning.
• Experience with SOA, REST APIs, MQs, and scalable architectures.
• Experience with AWS (EKS, Aurora RDS, Elasticache, DynamoDB) and containerization.

Responsibilities

• Define long-term technical vision and architecture for key services.
• Lead scoping, design, and implementation across multiple teams.
• Drive production rollouts to completion with minimal oversight.
• Mentor engineers and raise the technical bar across the org.

Skills

Java

Architecture

Mentoring

Distributed systems

REST APIs

AWS

CI/CD

Observability

Data pipelines

Spring

Containerization

Tools

Spring

Gradle

JUnit

AWS

EKS

Aurora RDS

Elasticache

DynamoDB

Kubernetes

Terraform

CDK

Job description

Flex is a growth-stage FinTech with NYC roots and teams across the US.

As a Staff Backend Engineer, you will design, build, and scale the services behind Payment, Billing, Identity, and partner integrations, setting the long-term technical vision and architecture for the systems you own, leading scoping, design, and implementation across teams, driving your own production rollouts to completion with minimal oversight, and working closely with product, design, and engineering peers to solve