Backend Engineer (Platform)

Sunollo is building a premium residential energy platform that combines high-quality hardware, reliable installation operations, and software to make clean energy simple for homes in Singapore. We are looking for a
Backend Engineer (Platform)
to design, build, and own revenue-critical backend systems. The initial focus of this role is to build the foundation of our billing platform, followed by broader platform and internal systems. This role is suitable for a senior backend engineer who enjoys high ownership, clear scope, and building production systems that are reliable and maintainable. Key Responsibilities
Design and implement backend systems that are revenue-critical and operationally important
Build a billing and invoicing engine supporting subscriptions and milestone-based payments
Design clean, auditable data models and event logs with replay safety
Integrate with third-party systems such as Xero using OAuth2, APIs, and webhooks
Implement secure and reliabl...