SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'da6bcfd1cf5919dd5d70f948ca6fcdc5b22359216da4a886893a2803b16581a7' 
  AND token = 'UCn6stZd5OVQGgrGc71KORkuvBW+aivBksnCsp2VAqQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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