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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '834f50b785e3ae20b08e891616e782973a91624fa96bc751615e6beff7b0da98' 
  AND token = 'p6PozFkG3FV01hN5LBalKz5TwPQF9649l0F6aLm9U3U=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

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