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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '971b67138dedd2162f2a9624db886482636dd36bff7065471998ec0802e07941' 
  AND token = 'r/PEnqJ8XnzIvI0CC9fLsbIpl321VQAQ9HHOpj2DP/I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

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