SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'bda9169d4ae23ee9a55002b3c514003987201a5d85cc3ff675459f9f87ee54c8' 
  AND token = 'L3/oXczOcRh5z2rS5EOmIbwfFZhuc87fUWx4x622Im4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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