SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12b37f7c342a19743f2d854ceff923e6edca95bbf4c1859d4a45da07deb28508' 
  AND token = 'gd9JHR/2WznfGYvpD81+cVsrp1KY5hjzsqrmp0DCuJI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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