SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f78ca356636866a915d7dd25b9654946be024934791f2fd1e97d259c7f9c63f' 
  AND token = 'DxAl3Ee/8CHk2idaTFETS4p2T0G4EgN7FNfRyqfQ8Yk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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