SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '94d23937d471854db24e227a282ab4c743b2ee21a54f4e74954b331241560f32' 
  AND token = 'py53qhBshHNyduVqi9IJk4eqKJUAZFKm27UgL6GgBKg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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