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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '340e610fc4637fcef063e77b3ae4b6a6ab16900c0d3bca39f559840cd5366da2' 
  AND token = '4FrhaAzMtgE0u62lTdLHnzqSmV53f01mTt6YqLfSris=' 
  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