SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'c986b635a210e0297b73df13771c60477190ef166ce4ec7a64035d0eb648baf6' 
  AND token = 'Aouk5waFfVmwy+xtzo0JtwCxDcdkMWPhvee2ksaZo3Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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