Senior Software Engineer-PHP

Who We Are

Finance leaders choose Billtrust to get paid faster, control costs, and maximize customer satisfaction. As the leader in B2B accounts receivable workflow and payment software, we provide the world’s leading brands with AI-powered solutions across the full AR lifecycle—from invoice presentment and payment processing to cash application and collections. With over 2,600 global customers, more than $1 trillion in invoice dollars processed, and a proprietary network of 13 million buyers, Billtrust delivers business value through deep industry expertise and a culture relentlessly focused on meaningful customer outcomes.

We’re an AI-first company, not just in what we build for our customers, but in how we work. Across every function, our teams use AI tools daily to work faster, make better decisions, and deliver higher-quality outcomes. We hire exceptional people, give them cutting-edge AI capabilities, and measure success by the impact they create. If you want to do the best work of your career at the frontier of AI and fintech, Billtrust is the place to do it.

Our Values

Customers

We relentlessly increase value for customer and do the right thing for them.

Action

We make ‘thoughtfully fast’ decisions, act quickly, cut through red tape, deliver progress not perfection, take ownership and accountability.

Team Spirit

We put the team ahead of ourselves, foster trust and respect, collaborate with passion, despise toxic politics, value our differences, and celebrate together.

Innovation

We challenge the status quo, experiment thoughtfully, and are novel and brilliant in what we create.

Excellence

We love to win, but we hate losing even more. We aspire to be the best and take pride in our work. When we fall short, we own it and come back stronger.

Senior Software Engineer, PHP

Job Summary

The Senior Software Engineer designs solutions and delivers features for our web applications using AI tools throughout the development lifecycle. As part of a small, collaborative cohart this position is accountable for features end-to-end leveraging AI assistance for specification, implementation, quality validation, deployment, and post-deployment support while ensuring quality outcomes at each stage. This role works primarily on web applications and services built on PHP, that integrate with other .net components also owned by the same team. The Senior Software Engineer interfaces with PO’s and fellow engineers to deliver scalable, performant web applications and services of high velocity. This position also helps evolve our AI-assisted development practices and mentors other Engineers on effective AI tool usage.

Job Responsibilities

• Own specification quality for assigned features and ensure specs are complete, unambiguous, and include acceptance criteria and edge cases.

• Collaborate with PO to translate product requirements into detailed technical specifications.

• Take ownership of domain knowledge within your cohort and share that knowledge and experience with the team.

• Use AI coding tools (Claude Code) to generate implementations from specifications.

• Design, build, support and maintain web application and service features that are performant, secure, and maintainable.

• Design performant software with a DevOps mindset that will scale as volumes increase.

• Review AI-generated code and peer contributions for correctness, security, and architectural alignment.

• Validate AI-generated tests and ensure comprehensive test coverage.

• Optimize queries, schemas, and storage strategies across relational MySQL and NoSQL datastores.

• Help evolve AI-assisted development practices including spec templates, prompt patterns, and validation workflows.

• Mentor other Engineers on effective AI tool usage and spec writing techniques.

Qualifications

Required

• Bachelor's degree in Computer Science (or equivalent experience) with strong understanding of data structures and scalable software design.

• 5+ years of relevant software engineering experience designing and implementing scalable web applications and services.

• Strong proficiency in PHP (Laravel/Kohana) and .NET (C#) development, with experience building scalable and maintainable web applications and services.

• Experience building software that is deployed to AWS - working with Terragrunt/Terraform and messaging platforms such as SNS/SQS, built on .net technology, to support cloud-native and event-driven architectures.

• Experience using testable application design principles.

• Strong understanding of SQL and relational databases, specifically MySQL, including schema design and query optimization.

• Knowledge of NoSQL data stores such as MongoDB or DynamoDB.

• Source control management using GitHub or similar.

• Experience with spec-driven, agentic AI workflows - working with AI coding assistants (Claude Code, Pi + OpenRouter or similar).

• Strong code review skills for AI-generated and human-written code.

• Proven experience contributing to development process improvements.

• Strong collaboration and verbal communication skills.

• Experience contributing to development process improvements.

Preferred

• Experience with message queues or streaming platforms (e.g., Kafka).

• Experience with PHP wrapper widgets (e.g., Kendo).