Software Engineer, Monetization Platform

Simular; Singapore; On-site; SGD 120,000 - 180,000; Full time

Job summary

Simular is building AI agents that help people and businesses get work done, with a focus on accounts, subscriptions, billing, and access provisioning. You will own domain models for customers, organizations, plans, and entitlements, and build robust billing systems with metering, invoicing, and failure handling.

You will partner with product teams to translate commercial requirements into maintainable systems while upholding high correctness and operational ownership in financial processes.

Qualifications

• BS/MS in Computer Science or equivalent experience.
• 5+ years of backend engineering experience in production systems.
• Experience building B2B SaaS or fintech systems.
• Hands-on Stripe experience including webhooks and life-cycle events.

Responsibilities

• Own domain models and APIs for accounts, organizations, and entitlements.
• Build billing systems including invoicing, proration, upgrades, and downgrades.
• Integrate Stripe and future providers across checkout and payments.
• Design idempotent, replay-safe, observable payment systems.
• Create reconciliation workflows, audit trails, and internal tools.
• Collaborate with product and customer teams to translate requirements.

Skills

Backend engineering

API design

Relational databases

Idempotency

Billing systems

Stripe experience

Education

BS/MS in Computer Science

Tools

Stripe webhooks

Job description

Where multiple locations are listed for this role, the position may be based in any of those locations, with priority determined according to the order of listing.At Simular, we are building AI agents that operate computers to help people and businesses get work done. As our product reaches more customers, we need the commercial systems that make product access, pricing, and revenue reliable. You will build the backend foundation that turns customer accounts and product usage into clear plans, accurate bills, successful payments, and correctly provisioned access. This is a SaaS monetization role focused on accounts, subscriptions, billing, payments, and entitlements. It is not an ads monetization role, and it is not primarily a cloud infrastructure or agent-runtime role.

What you'll do

• Own the domain models and APIs for customer accounts, organizations, workspaces, plans, pricing, trials, seats, and entitlements
• Build subscription and usage-based billing systems, including metering, aggregation, invoicing, credits, proration, upgrades, downgrades, cancellations, and recovery flows
• Integrate Stripe and future payment providers across checkout, recurring payments, payment failures, refunds, disputes, and provider webhooks
• Design robust payment and billing state machines that are idempotent, replay-safe, observable, and resilient to duplicate, delayed, or out-of-order events
• Build trustworthy financial records, reconciliation workflows, audit trails, and internal tools for resolving account and billing exceptions
• Partner with product and customer-facing teams to translate commercial requirements into simple, maintainable systems and customer experiences
• Set a high bar for correctness and operational ownership in systems where a wrong charge or missing entitlement directly affects customer trust

You might be a fit if

• You have a BS/MS in Computer Science or equivalent experience and 5+ years of backend engineering experience
• You have built production systems for B2B SaaS, e-commerce, fintech, or another transaction-heavy product
• You have hands-on experience with Stripe or a comparable payment provider, including webhooks, payment lifecycle events, and failure handling
• You can model complex business domains such as accounts, subscriptions, orders, invoices, payments, usage, and entitlements
• You understand idempotency, transactional consistency, money precision, reconciliation, auditing, and safe data migration practices
• You are strong with relational databases and production API design, and you can reason clearly about correctness under retries and partial failures
• You have a bias for action, communicate clearly, and enjoy owning an ambiguous 0 to 1 domain end-to-end
• Bonus: experience with usage-based billing, revenue operations, tax or invoicing systems, multi-currency payments, or financial ledgers