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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '596dafc81e053abaa5ac4ec2d8743dd1cf068dbde71f0f0b1d1c109381f0d623' 
  AND token = '483HcRr2sKVEHN09QXiDYeCas1nvfDMDxi7uTnwO9as=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

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