SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '400200507517fd5ae615cf803836c05d26f5ed1d1322d923ef833290c109e7ac' 
  AND token = 'AQBv0E2VOaVYZvtI4ENbnNUCKa2+PBcYRT1lrPjmG48=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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