Both appleIDs(create and modify/save) sign in iCloud. I use the following code to modify and save records: self.containerIdentifier).publicCloudDatabase database.fetch(withRecordID: CKRecord.ID(recordName:groupID), completionHandler: { record, error in if error == nil && record != nil { if let iDs : [String] = record!.object(forKey: "memberIDs") as? Array { if iDs.count < self.maxMemberCount { if let mems: [String] = record!.object(forKey: "memberNames") as? Array { if !(mems as NSArray).contains(name) { var members = mems members.append(name) record!.setObject(members as CKRecordValue, forKey: "memberNames") var iDs : [String] = record!.object(forKey: "memberIDs") as! Array iDs.append(self.myMemberID) record!.setObject(iDs as CKRecordValue, forKey:"memberIDs") database.save(record!, completionHandler: { record, error in if error == nil { } else { completion(error as NSError?) dPrint("Error : \(String(describing: error))") } }) }else{ let DBError : NSError = NSError(domain: "DBError", code: 89, userInfo: ["localizedDescription": NSLocalizedString("Your nickname already used.", comment:"")]) completion(DBError) print("change your nickname") } }else{ print("group DB error") let DBError : NSError = NSError(domain: "DBError", code: 88, userInfo: ["localizedDescription": NSLocalizedString("Please try later.", comment:"")]) completion(DBError) } } }else{ print("Error : \(String(describing: error))") } }) I received the following error message: ?Error saving records: <CKError 0x600000bbe970: "Service Unavailable" (6/NSCocoaErrorDomain:4099); "Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error."; Retry after 5.0 seconds> baseNSError@0 NSError domain: "CKErrorDomain" - code: 6 _userInfo __NSDictionaryI * 4 key/value pairs 0x000060000349e300 [0] (null) "NSLocalizedDescription" : "Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error." key __NSCFConstantString * "NSLocalizedDescription" 0x00000001117155a0 value __NSCFConstantString * "Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error." 0x000000011057e700 [1] (null) "CKRetryAfter" : Int32(5) key __NSCFConstantString * "CKRetryAfter" 0x000000011057c680 value NSConstantIntegerNumber? Int32(5) 0x00000001105c2ed0 [2] (null) "CKErrorDescription" : "Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error." key __NSCFConstantString * "CKErrorDescription" 0x0000000110568d00 value __NSCFConstantString * "Error connecting to CloudKit daemon. This could happen for many reasons, for example a daemon exit, a device reboot, a race with the connection inactivity monitor, invalid entitlements, and more. Check the logs around this time to investigate the cause of this error." 0x000000011057e700 [3] (null) "NSUnderlyingError" : domain: "NSCocoaErrorDomain" - code: 4099 key __NSCFConstantString * "NSUnderlyingError" 0x0000000111715540 value NSError? domain: "NSCocoaErrorDomain" - code: 4099 0x00006000016cc300