SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af1ace55c615d317684025337717eebdd672b8a68e265f308d243da8a87ea384' 
  AND token = 'MwzDNm8zgocyBx0SwVgW9lFewRSwyBDoseo/2e9tfTs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}