SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd52e0cfe5a212d34957a90fc957e9ae6584d1931ade903ad99f51a050746619b' 
  AND token = 'et3MYo8aZ2VioViadfyfbYbBP+3VLaWpUe0rHJ+A9v4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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