SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8b39c043c6b757940a37adb331654666730266afcd3b3d3972399cd74e9c5993' 
  AND token = 'QhWj3Zo2aixREeTM+S5V097+sDZbIPiXiUAVGQoRZoo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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