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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b51c9e460d1d89c32d646ddfcb2c201e5a0942bf03de39c299869601bb16ee5c' 
  AND token = 'm7FnbRVwHoG6XysEtGXuG3mSLmG4S58iP7e5706bCv8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00014

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