SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51bfe69322f3a81fa87a89ea06d6b2e8afdf2eeeeb041cc1ea38115284809534' 
  AND token = '716mkFd7DsklLtPQbcmXuQ95ryzNULJXjbLjkCcuC9o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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