SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9c5834c509216a48ec9dd21cd44693bb4d10df8abcf8593b01715b83f65a46c5' 
  AND token = 'w4mGUavVCluFX73wn8yj4smcOa/nBJmVStfBq+unZPk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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