SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bf8308464707e83b94f697f189abaefed75e5b5f17e94047fda26662bc6648db' 
  AND token = 'xMeu7fgrsYJzN1pmdh5gGQEzqkoe94tyCpexDq20j80=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00046

JSON explain

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