SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c438ef794e77f358d7d5a71e272450d2b33cc8b9fd9220b374c8db6a304e7951' 
  AND token = '83DHZRwHZrUcg/2N6PEic8CHJOvwCTKrvzMoVZuOk5I=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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