SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c523bb36532b7993d6b04efcb3026250579c8d2dd85e35909f0779dbb9d47a28' 
  AND token = 'lrSONfezfxYZelo9xwQPFca4Y7zadt7Ysc/w6tOVEwM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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