SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '2f042a42c37e406e9d6e5666f976906074e9ec5882dc57d97b49d15aeefba116' 
  AND token = '21In4h7udG8mEX825EPCZ1VP0eviZyZkaQ2lX/g+IsY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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