SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '3da1c75784c1a8af0be7c32512d686874c8859fa49db1ecbb8e98b75811fb8fb' 
  AND token = 't81tEJYOu3DzIak7PXOjRh5ww8m/L8V+uM+UggmRp3Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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