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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '391f287ea3c02802fcf8fd1dda757fb9b93d431d3e308bf2ea62fbbeeb70a2f5' 
  AND token = '+2PFxs2d9dAQCVbqlStpT6uj1DDMsqCK4fIKudeUYhw=' 
  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