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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8261b10ca23c3b4cbdf747d0b2725ad2c7d5e973318da55004a27507bff51e83' 
  AND token = 'nylIMyUoU5jt1zus1VghwuZc4bIftbMf81PJUjGPnyg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

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