Apple today informed developers that it will be conducting scheduled maintenance on Sunday, October 20 starting at 6 a.m. Pacific Time for up to eight hours, which will result in App Store Connect and the Developer ID notary service for notarizing Mac apps being unavailable during that time.
Apple says it apologizes for any inconvenience and recommends that developers make critical deliveries or changes on another day. Certificates, Identifiers & Profiles will remain available, according to Apple.
Apple's notary service for Mac apps experienced slowness last week, but it is unclear if the maintenance is related to that.
Developers are encouraged to monitor Apple's system status page.