SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = 'd26ea646c701c4974e1b822fa6df1ccde31ea7d07c954999bc21f085137b70f2' 
  AND token = 'N0TZ4iYWqgDCHKkBZo49+vZ+w4xjeNWz7jtvGSohuTc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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