SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '471cd8e4b6beaf7cc8584f3136ad59cc22a5b247146dd22ab65d971725908b8d' 
  AND token = 'jUD3RAnktzLz6w6SzmV+uceBYLm/rqenLm8KAfxTVJY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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