Migrating Counter Service storage: Design choices and learnings

Introduction Counter Service is used across Grab’s anti-fraud platform to answer time-windowed count questions, such as recent ride requests by a user or failed payment attempts on a card. The service handles tens of thousands of queries per second (QPS) with about a billion requests per day, while maintaining strict requirements around latency and reliability to support real-time fraud rule evaluation. For most of its life, Counter Service was backed by a wide-column database that served the workload reliably as the service scaled. As part of a broader infrastructure review mandated at an org