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Case study · Payments

Catch unusual transactions without blocking good customers

Fraud rules catch known patterns and block too many genuine customers. This is how we added machine learning risk scores to transaction processing, send uncertain cases to analysts and measure both fraud caught and customers wrongly stopped.

Project overview

Real-time risk scoring alongside existing rules.

Industry
Payments & lending
Client
Confidential
Solution
Anomaly and fraud detection
Platform
Azure ML + API
Timeline
12–18 weeks
Team
3–4 people
Latency
Real-time scoring
Review
Analyst queue
Governance
Model documentation and monitoring

Expected business outcomes

What the client set out to achieve

Measured on historical data first, then in shadow mode on live traffic.

  • 20–40% Fewer false positives at the same catch rate

    Fewer genuine customers stopped for the same fraud detected.

    Target range from shadow-mode comparison with current rules

  • Real time Scoring at transaction time

    A risk score returned within the payment flow.

    Latency budget agreed with engineering

  • Documented Model decisions

    Features, thresholds and performance recorded for audit.

    Model governance pack

Business challenges

Where the client started

Rules work, but they're blunt.

Rules

Dozens of rules added after each incident.

False positives

Genuine customers blocked and calling support.

Analysts

Review queues full of low-risk cases.

New patterns

Fraudsters adapt faster than rules are written.

Governance

Regulators expect decisions to be explainable.

Proposed solution

What the build covers

Machine learning alongside rules, with humans reviewing grey areas.

  • Feature engineering

    Behavioural features such as velocity, device and history.

  • Risk models

    Supervised and anomaly models scoring each transaction.

  • Scoring API

    Real-time scoring in the transaction flow with fallbacks.

  • Analyst queue

    Uncertain cases reviewed with reasons shown.

  • Shadow mode

    Models run silently alongside rules before they decide anything.

  • Monitoring

    Catch rate, false positives and drift tracked.

Project requirements

What the client asked us for

The request was to catch more fraud. Equally important is stopping fewer good customers, so both are measured from the start.

Models run in shadow mode first, compared with existing rules on live traffic, before they influence any decision.

What the project had to deliver

  • 01Risk scores in real time
  • 02Fewer genuine customers blocked
  • 03Analysts on the right cases
  • 04Explainable decisions

Key challenges & considerations

What made it harder, and what we did

  1. Few confirmed fraud labels

    What we did

    Anomaly detection and analyst feedback were used while confirmed fraud labels were still scarce.

  2. Strict latency requirements

    What we did

    The scoring service was built and tested to the latency budget.

  3. Regulatory explainability

    What we did

    Every alert carried its reasons, and the models were documented for audit.

  4. Adversaries changing behaviour

    What we did

    Models ran in shadow mode first and were retrained as patterns changed.

What we watched for

  • Measure false positives, not just fraud caught
  • Always run in shadow mode first
  • Document models for audit
  • Retrain as patterns change

Development process

Shadow first, then decide

No customer is affected until the model has proved itself.

  1. Stage 1

    Data and labels

    Transactions and confirmed outcomes prepared.

  2. Stage 2

    Models

    Models built and validated on historical data.

  3. Stage 3

    Shadow mode

    Live scoring alongside rules without affecting decisions.

  4. Stage 4

    Decision rollout

    Thresholds set with fraud and product teams.

  5. Stage 5

    Monitoring

    Ongoing tracking and periodic retraining.

Technology stack

Real-time ML scoring

Low-latency scoring with full audit trails.

Machine learning

  • Python
  • scikit-learn / LightGBM
  • Azure Machine Learning

Data

  • Microsoft Fabric or Azure SQL
  • Feature pipelines

Serving

  • Batch scoring
  • REST API
  • ERP/CRM integration

Monitoring

  • Accuracy tracking
  • Drift alerts
  • Retraining schedule

Quality assurance & deployment

Measured against a test set before launch

AI quality was measured, not judged from a demo. A test set of real examples with agreed answers decided whether the system was ready, and the same set was re-run after every change.

  • A test set of real examples with agreed answers
  • Accuracy thresholds agreed with the business before launch
  • Safety checks: refusals, permissions and prompt-injection tests
  • A person reviewing low-confidence output
  • Cost and response time measured at real volumes

Deployment

  • 01Decision rolloutThresholds set with fraud and product teams.
  • 02MonitoringOngoing tracking and periodic retraining.
  • 03Pilot, then staged rolloutA small group of real users first, with results reviewed weekly before widening access.
  • 04Monitoring and warrantyAccuracy, drift, usage and cost tracked after launch, and six months of free bug fixing.

Final deliverables

Sharper decisions, fewer blocked customers

Transactions are scored in real time, clear cases are handled automatically and analysts focus on genuinely uncertain ones.

Every decision is documented and performance is monitored continuously.

  • Real-time risk scores
  • Shadow-tested models
  • Focused analyst queues
  • Audit-ready governance

Handed over to the client

  • 01Production AI serviceDeployed in the client's own cloud tenant
  • 02Source code and modelsIn a repository the client can access
  • 03Test set and resultsThe evidence behind the launch decision
  • 04MonitoringAccuracy, usage and cost
  • 05Six-month warrantyFree bug fixing after delivery

Success metrics

How success is measured

MeasureOutcomeHow it is measured
Fewer false positives at the same catch rate 20–40% Target range from shadow-mode comparison with current rules
Scoring at transaction time Real time Latency budget agreed with engineering
Model decisions Documented Model governance pack

Verified reviews

What clients say about our custom software work

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