SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'af519bf05f3c152970684e13ac821e77a23b368d7535dd7ebb53ed8a6eeca371' 
  AND token = 'Ro9bJE9MsQfIroTlcMmrwTRyolKwNFnWXL51taOf+D4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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