Senior Software Engineer — B2B Payments Product - (HR70506)

Company Overview:

Sagan is an exclusive membership community for top executives, founders, and CEOs seeking to hire and maximize the impact of international talent. We bridge the gap between global talent and US-based businesses, connecting candidates from vibrant regions like Latin America, the Philippines, India, Pakistan, Bangladesh, and Africa with leading American companies. Sagan provides a high-performance remote work environment, ensuring access to world-class opportunities for top-tier professionals.

Position Overview:

We are building a B2B payments product that sits between finance teams and their bank. The product turns a manual, error-prone, high-fraud-risk payment workflow into a controlled, auditable batch process. The first version takes approved vendor payments and outputs a structured electronic file that the bank ingests for batch processing.

Security and control sit at the center of the product. Multitenant from day one. Dual approval on payments. Authorization workflow on any change to vendor bank details. Role-based access with 2FA where it matters. You would own the v1 build end to end.

What you will build in v1:

• A multitenant Postgres-backed vendor database with strict per-tenant isolation, configurable fields, and a separate authorization workflow for any change to a vendor's bank details.
• Role-based authentication with three roles (Viewer, Submitter, Approver) and 2FA enforced for Approvers and admins.
• A payment intake flow where Submitters select vendors, enter amounts, and create batches that group by currency.
• A dual-approval queue where Approvers verify and authorize batches with 2FA, with rejected batches returning to Submitters with comments.
• A deterministic electronic payment file generator that outputs a fixed format the receiving bank expects, with a complete audit trail and timestamped payment records.
• A clean, bank-grade dashboard UI in HTML, CSS, and JavaScript that reads as trustworthy to finance professionals.
• A working reference implementation of the file format already exists. You will use it as the spec rather than reverse-engineering anything from scratch.

What success looks like?

• A finance team can run their full monthly payment cycle end to end through the product.
• Zero unauthorized changes to vendor bank details pass through the workflow.
• The architecture supports a second tenant onboarding without code changes.
• A clear path to v2 is documented and partially scaffolded, including an automated portal upload flow via browser agent and an accounting platform integration.

Required technical skills:

• 5+ years building production web applications, with at least one project where you owned multitenant data isolation.
• Strong Python for backend and API work.
• Postgres at a working depth: schema design for tenant isolation, row-level security, indexes, migrations.
• Authentication and authorization patterns including RBAC, 2FA (TOTP and email-based), session security, and password hygiene.
• Experience writing deterministic file generators against a fixed institutional format (NACHA, ISO 20022, BACS, EDI variants, regulatory CSV formats, anything similar).
• Audit logging and change history patterns for regulated or finance-adjacent products.
• Comfort deploying on Railway, Fly, Render, or equivalent with managed Postgres.
• Frontend competence with vanilla HTML, CSS, and JavaScript, or a framework you can ship cleanly without ceremony.

Required mindset:

• AI-native by default. Claude Code is your daily driver. You design with MCP servers in mind and know when to reach for an agent versus when to write the code yourself.
• Security is a feature. You read the threat model into the requirements and push back if a workflow opens fraud risk.
• You ship simple things end to end before you ship clever things halfway.
• You write tight, readable code, leave a maintainable surface, and document your design choices for the next engineer.

Nice-to-Haves:

• Prior payments, banking, or accounting integration experience.
• Playwright or browser agent experience for v2 automated portal work.
• Background as a founder, solo agency operator, or small AI agency CEO.

Engagement and rate:

• Project-based contract for v1, with a retainer option afterward for v2 and ongoing maintenance.
• Rate is set during the screening conversation and reflects the senior nature of the work.
• Payment is split across project milestones.

How to apply:

Send the following through the Calendly intake:

• LinkedIn profile
• GitHub profile. We look at contribution activity, personal tools, and any product you have shipped on your own.
• A screenshot of your AI coding usage from the last 30 days (Claude, Cursor, or equivalent).
• 3 to 5 million tokens per day is the baseline we look for.
• A link to one production project you owned where you handled authentication, multitenancy, or financial data.

Work Location: Remote