About usClimate & Decisions is a Sydney-based advisory firm founded in 2024 by former Deloitte and SAP leaders. It is a member of the Stone & Chalk innovation hub.

We are building an enterprise software platform for large to medium organisations:

- Live in production on AWS. Enterprise customer onboarding starts in January 2027.
- Multi-tenant B2B SaaS. Each customer has an isolated environment.
- Independent engineering audit completed in October 2026. Its findings are your starting backlog.
- Stack: Python / FastAPI, PostgreSQL with row-level security, vanilla JavaScript, AWS (ECS Fargate, RDS, Bedrock, CloudFormation), GitHub Actions.

We share product details after a mutual NDA. What you'll do before ChristmasBy early December the critical fixes are done and the platform goes through a penetration test. By Christmas the foundations are signed off by you, ready for customers in January.
1. Review the code and the audit. Read the codebase and the independent engineering audit. Confirm, re-prioritise and own the fix plan.
2. Be the reviewer on every change. Review and approve all pull requests before they reach production.
3. Harden security. Check tenant isolation (row-level security, database roles), login and MFA, roles and permissions, secrets, and the guardrails around AI features.
4. Make releases safe. Set up database migrations, a staging environment, deployment checks, monitoring and alarms, and backups with a tested restore.
5. Add automated checks. Security and dependency scanning in CI, alongside the existing tests.
6. Prepare for the penetration test. Get the platform ready for an external penetration test in early December 2026, then fix what it finds.
7. Document it. Write a short incident runbook and the security answers enterprise customers ask for.
8. Plan 2027. Deliver a prioritised engineering roadmap for the next 6 months.

What you'll bringMust have

- 10+ years building and running production software,



including multi-tenant B2B SaaS.
- Strong Python (FastAPI, Django or Flask) and PostgreSQL: row-level security, roles, migrations.
- AWS in production: ECS/Fargate, RDS, IAM, CloudFormation or similar infrastructure as code.
- Application security: OWASP Top 10, authentication and MFA, secrets management.
- CI/CD with GitHub Actions, and a disciplined pull-request review practice.
- Comfortable working with tools like Claude Code.
- Explains technical risks clearly to a non-technical founder.
- Right to work in Australia.

Nice to have

- SOC 2 or ISO 27001 experience.
- Security of LLM features (prompt injection, data leakage), ideally on AWS Bedrock.
- Testing calculation-heavy or financial systems.
- Fractional CTO or technical advisor experience with startups building scalable SaaS solutions.

Beyond ChristmasThere is a transparent opportunity to continue part time in 2027, at about 1 day a week, as the platform's trusted technical owner.
- Remain the required reviewer on code changes and the security owner.
- Oversee the penetration retest and any remaining fixes.
- Run quarterly backup-restore drills and dependency and security reviews.
- Give architecture guidance and light-touch review of a junior developer's work.
- Be on call as backup during customer go-lives.

As enterprise customers sign, the role can grow to 2–3 days a week or a fractional technical lead position. Terms and how to apply
- Start: as soon as possible in November 2026.
- Rate: A$1,100–1,300 per day + GST, ABN contract, depending on experience.
- Before access: mutual NDA and IP assignment for work delivered.
- Working pattern: flexible days, with some overlap with Sydney business hours.

To apply, email [email protected] with the subject "Senior Software Engineer" and include:
1. Your CV or LinkedIn profile.
2. One paragraph on a SaaS security or code review you led, and what you found.
3. Your availability (days a week, from when) and your expected day rate within this range.

📌 Senior Software Engineer (part-time contract) (Sydney)
🏢 Climate u0026 Decisions
📍 Sydney