Monitoring and alerting ensure that system behavior and transaction processing are continuously observed, evaluated, and acted upon in real time.

They enable the Merchant to detect anomalies, respond to operational issues, and maintain reliable transaction processing under both normal and exceptional conditions.

Monitoring Principles

Monitoring must provide continuous visibility into system behavior and transaction activity across all processing stages.

• The Merchant system must:
  • Monitor all relevant transaction flows and system components
  • Track key operational signals across API interactions, asynchronous processing, and internal operations
  • Ensure that monitoring reflects real-time system state

Monitoring must enable early detection of:

• Failed or degraded transaction processing
• Abnormal system behavior
• Inconsistent or incomplete transaction flows

Monitoring must be designed as an integral part of the system, ensuring that critical conditions are observable as they occur.

Key Monitoring Signals

Monitoring must be based on meaningful and actionable signals.

• The Merchant system must monitor:
  • Error rates and failure patterns
  • Transaction processing latency and delays
  • Retry frequency and abnormal retry behavior
  • Volume and distribution of transaction activity
  • Asynchronous event patterns (e.g., delayed or duplicated notifications)

These signals must provide sufficient visibility to identify deviations from expected system behavior.

The interpretation of transaction outcomes and states must follow the model defined in F.3 Success and Error Scenarios, ensuring that monitoring reflects actual business outcomes and not only technical responses.

Detection of Anomalies

Monitoring must support the detection of abnormal conditions

• The Merchant system must:
  • Identify deviations from normal transaction patterns
  • Detect repeated failures or unexpected system responses
  • Recognize inconsistencies in transaction progression

Anomalies may include:

• Sudden increases in error rates
• Unexpected transaction states
• Missing or delayed asynchronous events

Early detection of anomalies is essential to prevent operational degradation and financial impact.

Alerting Principles

Alerting must ensure that critical issues are promptly communicated and acted upon.

• The Merchant system must:
  • Generate alerts based on defined conditions and thresholds
  • Ensure that alerts are actionable and relevant
  • Avoid excessive or redundant alert generation

Alerts must be:

• Timely, reflecting real operational conditions
• Prioritized according to severity and impact
• Directed to appropriate operational teams

Ineffective alerting may lead to missed incidents or alert fatigue, reducing the effectiveness of monitoring systems.

Correlation with Transaction Context

Alerts and monitoring signals must be correlated with transaction context.

• The Merchant system must:
  • Associate alerts with the relevant transaction or set of transactions
  • Ensure that monitoring data can be linked to specific events and execution flows
  • Use consistent identifiers to relate alerts to logged events

Correlation practices defined in F.5.2 Correlation and Traceability must be applied to ensure that alerts and monitoring data can be accurately interpreted.

Monitoring of Asynchronous Processing

Asynchronous processing requires dedicated monitoring considerations.

• The Merchant system must:
  • Monitor the reception and processing of asynchronous notifications
  • Detect delayed, duplicated, or missing events
  • Identify inconsistencies between asynchronous updates and expected transaction progression

Monitoring must ensure that asynchronous behavior is visible and can be reconciled with the overall transaction lifecycle.

Operational Response

Monitoring and alerting must support effective operational response.

• The Merchant system must ensure that:
  • Detected issues can be investigated using logs and correlated data
  • Alerts trigger appropriate diagnostic and recovery actions
  • Monitoring supports decision-making during incident handling

Effective response depends on the integration of monitoring, logging, and correlation capabilities across the system.

Reliability of Monitoring Systems

Monitoring and alerting systems must be reliable and consistently available.

• The Merchant system must ensure that:
  • Monitoring is continuously active across all environments
  • Failures in monitoring systems are detected and addressed
  • Alerting mechanisms remain functional under failure conditions

Gaps in monitoring or alerting may result in undetected issues and delayed response.

Key Principle

Monitoring and alerting must be enforced as system-wide operational capabilities, ensuring that all relevant system behavior and transaction activity can be detected, evaluated, and acted upon in real time, supporting reliable and consistent operation under real-world conditions.