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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '255665203492e8b861b026e6d822bb9f9d171e7e2dfd5b6b2f02742a9e736dec' 
  AND token = 'tGqo6vG2ktgRrbkBzP37PdMqdXUPlcT7b77ZJn3qv1k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00186

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