SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'a6537dc392ccb6565cf3aa78c6b3a27cf09a0e9b44b13e215ab64f02698958a8' 
  AND token = 'Py7tOkGx0j1GsxbfuxAbusqJkYGzZHRm1a/JtvXgnUg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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