Backend Engineer (Django / Python)
Celsus is built on a Django REST backend that handles lease lifecycles, rent collection, payment reconciliation, and multi-tenant access control — all at once. Every new feature touches real money or real obligations. You will design and implement the API and data layer for the platform's most consequential workflows, working closely with the frontend and mobile teams from contract definition through to production.
Responsibilities
What you will own
Design and build REST API endpoints across core domains — leases, payments, maintenance, documents, and subscription billing — with correctness and backward compatibility as non-negotiables
Own the data model for new features: schema design, migrations, and query performance from day one
Implement and maintain business logic for financial workflows including payment state machines, proration, grace period enforcement, and audit trail integrity
Write integration and unit tests that cover the edge cases that matter — concurrent writes, partial failures, and state transitions — not just the happy path
Review API contracts with frontend and mobile teams before implementation begins and hold them through delivery
Requirements
What we are looking for
3+ years of professional backend development with Django and Django REST Framework in a production SaaS
Strong command of PostgreSQL — query optimisation, indexing strategy, and safe migration practices under live traffic
Experience designing for multi-tenancy: row-level data isolation, scoped permissions, and org-level access control
Familiarity with background task processing using Celery or an equivalent — scheduling, retries, and failure handling
An instinct for financial correctness: idempotency, decimal precision, and the implications of getting a calculation wrong at scale
Backend Engineer (Django / Python)
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