SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '840a242ffa9729d5a50ae51c18294f43391066c00b112d754b347fefe6591fe2' 
  AND token = 'fH99474Rf6qy/ByH6NW0LbRgFjGHEiQgTC5bwNLFiEw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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