Core Architecture & Payment File Standards
Secure delivery, NACHA layouts, ISO 20022 vs legacy formats, and the structural rules every payment pipeline must respect.
Banking ACH & Wire reconciliation,
automated with production Python.
For bank ops, payment engineers, FinTech devs and Python automation teams.
A hub of engineering-grade material for teams that own real payment pipelines. Every page is written from the perspective of an on-call engineer wiring up NACHA ingestion, normalizing ISO 20022 messages, or chasing a reconciliation break before settlement cutoff — not a tutorial walkthrough.
The site bundles parsing, matching, exception handling, fraud-pattern detection, and Reg E/Fed-aligned audit practices. Code is shippable Python (pandas, pydantic, asyncio, polars), and procedures map directly to NACHA Operating Rules, ISO 20022 messages, and Reg E timelines.
Automated File Ingestion & Parsing Pipelines
Streaming fixed-width decoders, pandas/Polars throughput tuning, pydantic validation, async batch orchestration.
Transaction Matching & Reconciliation Algorithms
Deterministic and fuzzy matching, sliding date windows, tolerance thresholds, multi-field fallback chains.
Start here
Six deep-dives that cover the seams where real reconciliation pipelines break — pick the one closest to what you are wiring up today.
- Implementing SFTP with PGP for ACH Files Secure the ingestion boundary: keyed SFTP transport plus PGP encryption for NACHA deliveries.
- ISO 20022 pain.001 Parsing in Python Streaming XSD validation and namespace-aware extraction for credit-transfer initiation messages.
- Optimizing pandas read_fwf for 1GB NACHA Files Throughput tuning for fixed-width decoding when batch files run into the gigabytes.
- Validating NACHA Addenda Records with Pydantic Model addenda structures and reject malformed records before they reach matching.
- Implementing Levenshtein Distance for Payment References Fuzzy-match noisy remittance strings without auto-resolving a duplicate.
- Configuring Rolling 3-Day Reconciliation Windows Align settlement timing across ACH and wire with a sliding date window.
What's inside
The hub is organised around three engineering disciplines that every reconciliation team has to master. Each section maps to a directory of deep-dives with runnable code and the regulatory context that surrounds it.
- Architecture: secure ingestion boundaries, NACHA record layouts, ISO 20022 vs legacy.
- Ingestion: streaming fixed-width decoders, pandas/Polars throughput, pydantic validation, async batch.
- Matching: deterministic vs fuzzy logic, sliding windows, tolerances, multi-field fallback chains.
Why this exists
Most public material on payment automation is either a marketing piece or a 10-line snippet. Real pipelines fail at the seams — encoding drift on bank exports, batch headers that don't reconcile, fuzzy matches that auto-resolve a duplicate, Reg E timers tripping on stalled exceptions. The content here is written to be a reference you keep open while you fix those problems.