# Senior Ledger Engineer

> The ledger is the heart of CorebankOS. Every card authorisation, SEPA transfer and interest accrual across our banks lands here as a posting - and it has to be correct, auditable and fast, every single time.

Source: https://corebankos.com/company/careers/senior-ledger-engineer

Own the double-entry ledger that every CorebankOS bank runs on - every balance, every posting, in real time. Kotlin, PostgreSQL and a lot of care about money.

## About the role

The ledger is the heart of CorebankOS. Every card authorisation, SEPA transfer and interest accrual across our banks lands here as a posting - and it has to be correct, auditable and fast, every single time.

You’ll join a team of five engineers who own the ledger end to end: the posting engine, balance projections, reconciliation and the APIs the rest of the platform builds on. Small team, real banks, your name on the launch.

## What you’ll do

- Design and evolve the posting engine - idempotent, double-entry, with strict ordering guarantees.
- Build real-time balance and limit projections that serve thousands of requests per second.
- Own reconciliation with card schemes and payment rails, and make breaks impossible to miss.
- Shape the ledger APIs used by mobile, web banking and the backoffice.
- Join bank launches and be there when the first real payment lands.

## What you’ll bring

- 5+ years building backend systems in Kotlin, Java or another JVM language.
- Deep PostgreSQL experience - transactions, isolation levels, partitioning, query plans.
- You’ve shipped systems where correctness matters more than speed - and then made them fast.
- Comfortable with event-driven design, outbox patterns and exactly-once processing trade-offs.
- Clear written English; you enjoy explaining hard things simply.

## Nice to have

- Experience in core banking, payments or accounting systems.
- Familiarity with ISO 20022, SEPA or card scheme settlement files.
- You’ve worked under PCI DSS, DORA or SOC 2 controls.

## Your stack

Kotlin, PostgreSQL, Kafka, gRPC, Kubernetes, Terraform, OpenTelemetry