SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '9d9853088127360f55871d31190bdf6054a73e8738724fa47b8498d990f4bb2f' 
  AND token = '3TSlaBHOghTXKJApcgTC5BUjlzg18tsw+TlglpdOGI0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00012

JSON explain

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