rosscyking/responsible-neobank-growth-events

Responsible Neobank Growth — Synthetic Event Benchmark

A synthetic dataset of neobank service events that misbehave on purpose — late, duplicated, reversed, schema-evolving — with the correct answer known in advance. It is built for testing incremental pipelines, data contracts, referral-reward reconciliation, data quality and BI, where you want to check a warehouse's output against a fixed truth rather than eyeball it.

Fully synthetic. No affiliation with Monzo or any bank; no real customer, internal, or proprietary data. The identifiers are salted hashes, not people. Do not treat any of it as representative of a real population.

What it's for

Turn messy backend events into interfaces you can trust, and check that an incremental warehouse gives the same answer as a full rebuild. The events back four governed questions: growth acquisition, referral economics, reward reconciliation, warehouse health.

What's inside

data/<profile>/*.jsonl     immutable ingestion-day delivery batches (envelope + payload)
truth/<profile>-manifest.json   the exact expected outcomes (counts, duplicates, quarantine, ledger, exceptions)
schemas/                   event envelope + payload JSON Schemas + registry
configs/                   generator profile configs (seed, clock, scenario mix)
checksums/SHA256SUMS       per-file checksums
examples/validate_truth.py recompute the observable facts and check them against truth
build-manifest.json        generator version, profiles, logical checksums, licence

Every event shares one envelope — event_id, idempotency_key, event_name, occurred_at/emitted_at/ingested_at in UTC, schema_version, payload — with money in integer minor units.

Why the schema is pinned in this card

payload is a union: its fields depend on event_name, and referral-qualified appears under both schema_version 1 and 2 with different fields. That is the dataset's subject matter, not an accident.

It does mean the shape cannot be inferred per file. Each day's file contains a different mix of event types, so inferring separately gives a different payload struct per file — and a field that happens to be absent from one day infers as null, which will not merge with a string. Reading the files together then fails with an Arrow schema-mismatch error, which is what breaks a preview.

So this card declares the full union explicitly in dataset_info.features: the 30 payload fields across all event types, each with one consistent type. Every file is cast to that one schema, and a field an event does not carry reads as null. Do not remove this block. Without it the dataset still downloads, but the viewer and a plain load_dataset over multiple files will fail to unify the schema. If a new event type or payload field is ever added, add it here too.

Profiles

Profile	Deliveries	Use
tiny	~1.8k	contracts, CI, a quick look (shipped with the repo)
standard	~569k	pipeline and benchmark scale (built on demand; same logical checksum across runs)

The injected failures

Faults go in after valid generation, so the truth stays separable from the defects: duplicate deliveries sharing an idempotency key, late and beyond-lookback arrivals, reward reversals, malformed payloads sent to quarantine, v1 and v2 schemas side by side, a freshness outage, and reconciliation breaks. truth/<profile>-manifest.json states the exact expected counts, lifecycle end states, ledger totals and exception reason codes.

Reproducibility

Seeded generators on a virtual UTC clock — no wall clock, no random UUIDs. The same profile config reproduces the same logical content: two independent standard runs gave the same logical checksum. Generator version and seeds are in configs/ and build-manifest.json.

Validation

Recompute and compare against the truth manifest with examples/validate_truth.py, plus the repository's contract, oracle and blue/green tests. The base/delta/repair splits are pipeline-processing phases, not ML train/validation/test.

Limitations

Volumes, rates and amounts are engineered for coverage and are not calibrated to any bank. The reward accounting is an illustrative double-entry treatment, not any real institution's policy. Do not infer anything about real customers or populations from it.

Intended and prohibited uses

Use it for data-engineering teaching, incremental-pipeline and backfill testing, reconciliation and data-quality demos, and BI or semantic-layer demos. Do not use it for lending, fraud or AML decisions, customer profiling, regulatory reporting, or any claim about real populations — it cannot support those and must not be used for them.

Licence and citation

Data: CC-BY-4.0. Code (repository): MIT © 2026 Cheng-Yuan King. Please cite the repository and commit. No affiliation with Monzo Bank Ltd is claimed or implied.

Provenance

Generated by the Responsible Neobank Growth project. The repository commit and per-file checksums are in build-manifest.json and checksums/SHA256SUMS. Issues go to the repository's tracker.