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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5b76d52a11a698ca8b26e35e5f130fa4ca60bad7f014f9208538b34864a9c569' 
  AND token = 'KMh6RQml12cJmGE4rlSaJykTGut7Vf7+3pojJI+IVlg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

Explain
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE								Impossible WHERE noticed after reading const tables