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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a121d641a8a0291d29688df8be5aaae435a5d6e2351f482da86075deef958fe1' 
  AND token = 'GSI/Uy/QzUiJpRffWdpY1CVQUe77ot9B011by6yTgfY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

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