Beyond interbank: Identifying critical participants in integrated RTGS systems using payment type and temporal dynamics

As modern economies increasingly adopt digital and instant payments, ensuring the resilience of payment systems and maintaining public trust have become more critical. This paper extends the network and clustering approach of Glowka et al. (2025) to identify critical participants in real-time gross settlement (RTGS) systems - those whose failure could disrupt system continuity. Our extension incorporates three key dimensions: payment type (interbank vs. customer), intrayear temporal frequency, and transaction view (value vs. volume). With these dimensions, we derive an extensive set of granular criticality scenarios and weight each scenario result by its economic activity to reflect its operational relevance. Applying this method to transaction data from SIC, Switzerland's RTGS system, we find that, beyond large international banks, mid-sized domestic banks and, occasionally, financial market infrastructures also play critical roles, especially during periods of heightened economic activity and night-time settlement hours. These criticality results are consistent, although some participants feature more prominently in the volume-based view. Our findings provide system operators and regulators with complementary tools to meet the Principles for Financial Market Infrastructures (PFMI), enabling context-specific assessment of criticality in RTGS systems and informing realistic stress test scenarios amid a rapidly evolving payment landscape.