As long as your eligibility system is in conformance with the CAQH CORE 157 Rule, then it is not required to send back an eligibility response, either in real time or batch.

Partially. CORE-certified health plans (or information sources), clearinghouses/switches or other intermediaries must publish their regularly scheduled system downtime in an appropriate manner (e.g., on websites or in Companion Guides). This allows the healthcare provider to better manage staffing levels. Additionally, the CAQH CORE 157 Rule outlines requirements for reporting/publishing non-routine downtimes, and unscheduled/emergency downtimes.