Engineering Senior Backend Engineer — Ledger Remote (US)

A8 Core; Northern (KY); Remote; USD 120,000 - 180,000; Full time

Job summary

Financial Infrastructure, Inc. is seeking a senior backend engineer to own the ledger subsystem for the A8 Core platform. You will design and implement services in .NET that guarantee exact-once posting, correct balances, and scalable performance under load.

Remote work within the United States is available. You will collaborate with Compliance and Engineering to ensure auditability and reliability of the dual-entry ledger across deposits, transfers, and directives.

Qualifications

• 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.

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.

Skills

C#

.NET

SQL

Concurrency

Idempotency

Tools

ServiceStack

PostgreSQL

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.