SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9256c8a3a5270bddf049fb1f6c0ffe1f8ce7cce86c1a667a304ea869f13494e3' 
  AND token = 'LB/3soZmViECsQw+3eVvILvVIedGnORXgC71juRORLE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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