Optimize for performance

I notice that many of mysql slow queries come from ultimate cron related activities:

INSERT INTO background_process (handle, start_stamp, exec_status) VALUES('uc:media_youtube_cron', '1470393302.715884', 1);
UPDATE background_process SET start_stamp = '1470393004.233479', exec_status = 2 WHERE handle = 'uc:file_cron' AND exec_status IN (1, 3);
UPDATE variable SET value = 'i:1470393004;' WHERE name = 'cron_last';
INSERT INTO ultimate_cron_log (name, start_stamp, end_stamp, service_host, exec_status, severity, msg) VALUES ('signup_cron', 1470392703.7728, 1470392703.8235, 'default', 1, -1, '');
SELECT handle, callback, args, uid, token, service_host, start_stamp, exec_status FROM background_process WHERE handle = 'uc:oauth_common_cron';
INSERT INTO variable (name, value) VALUES ('cron_semaphore', 'i:1470391802;');

Why are these queries so expensive?
Isn't default scheduling */10+@ * * * * way to aggressive?
Any advice to reduce cron footprint welcome.

Thanks