SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '15d59af2a1ff034e2407b9c22ed97517213a0b6a68b271a5293b705a01ca4857' 
  AND token = 'qaQ389IC+reNf1+KGMLHlmk3RUmazhTKeswtdrTsnsU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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