SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '9e70116396e4620ad9cb20d4e5da0602cb06c9a6cbea3da5d42435a5a2af0126' 
  AND token = 'TfNxcqf0qhPWmaOrZWHVGQMIsZvnyUCh5SjpKKZ4/TM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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