About this opportunity
A8 Core lists this Engineering Senior Backend Engineer — Ledger Remote (US) opportunity in northern, Kentucky. Review the employer’s description below for duties, qualifications and application requirements.
Job description
Service status · A8 Core™ · The Operating System for Financial Accounts · The account operating system · API-first
Own the double-entry ledger at the core of every A8 Core™ account — the one component that is never allowed to be wrong.
Location Remote (United States) Reports to Principal Software Architect Team Engineering
Own the double-entry ledger at the core of every A8 Core™ account — the one component that is never allowed to be wrong.
Every balance, every deposit, every transfer, and every directive on the platform resolves to an entry in the ledger. It is the system of record that customers, auditors, and regulators ultimately trust. This role owns the correctness, performance, and auditability of that ledger: exactly-once posting, immutable history, and balances that are right to the cent under load.
What you’ll own
Double-entry posting, balance computation, and the immutable transaction history.
Exactly-once semantics and idempotent posting keyed to the caller’s ProviderReferenceId.
Transaction processing
The lifecycle of deposits, withdrawals, transfers, and account directives from acceptance to settlement.
Integrity & audit
Reconciliation between the ledger and external rails, and the append-only evidentiary record that proves every posting.
Performance & scale
High-throughput posting, partitioning, and the data model that keeps it fast as account volume grows.
Responsibilities
Design and build ledger services on .NET 10 that post transactions correctly and idempotently.
Guarantee exactly-once posting and consistent balances under concurrency and retries.
Implement reconciliation and integrity checks against funding rails and account state.
Write the append-only evidentiary record alongside every state change, keyed to the RequestId.
Partner with Compliance on the audit and reporting needs the ledger must satisfy.
Hold the correctness bar through rigorous testing, property-based checks, and code review.
Qualifications
Required
6+ years building backend services in production, with significant time on systems where correctness is non-negotiable.
Strong .NET / C# and relational data modeling (SQL Server or PostgreSQL).
Deep, practical understanding of idempotency, concurrency, transactions, and consistency.
Experience with financial ledgers, payments, or other transaction-of-record systems.
Preferred
Hands‑on experience designing double-entry accounting or ledger systems.
Event‑driven and event‑sourced architectures at scale.
Familiarity with ServiceStack and high‑throughput payment processing.
Technical environment
Core
Data
Infrastructure
Practices
Idempotency Event sourcing Reconciliation
Your first year
First 90 Days
Ship your first ledger improvements and develop a deep model of how posting and balances work.
First 6 Months
Lead a ledger subsystem end to end and measurably strengthen reconciliation and integrity.
First 12 Months
Own the correctness and performance roadmap for the ledger as account volume scales.
Join the team
Why join A8 Core™
The ledger is the part of fintech that has to be exactly right, every time. You will own the component the entire platform’s trust rests on — and build it to a standard that holds for decades.
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Who can apply
Review the original listing for work authorization, qualifications and employer requirements.