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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68393c1bcb13e1dd9192b8eed6c9f35fffd5f54ecbbcc38a0339af8464e79902' 
  AND token = '5P9cuOCiaABuH2S4gVO3WmPBFWzSRvFB0dkm6PN5ZNw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

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