rate limiting w/ enterprise

Nobody has claimed this yet.

I have been trying to use the isochrone API to generate 10-minute walking isochrones using a list of coordinate pairs but my attempt fails even while iterating over a small number (such as 5) points. I have an enterprise account so should there should be a very high rate limit.

The script will execute the first time on 5 points, but on the second try and subsequent tries, it will throw the following error from **isochrone.js** :

'data': resp.durations[0],
^
TypeError: Cannot read property 'durations' of undefined

If I include a geojson with many points (such as 100), it will fail every time.

Any ideas on how to solve this?
I have included both the geojson that I am iterating over and the modified index.js file below:

index.js

```
isochrone = require('./isochrone.js');
var turf = require('@turf/turf');
var fs = require('fs'),
obj

token = 'mytoken'

fs.readFile('poi.geojson', handleFile);
fts = []

function handleFile(err, data) {
if (err) throw err
obj = JSON.parse(data)
features = obj.features
console.log(features.length)

for (var j = 0; j = features.length){console.log('made it to the end')

var collection = JSON.stringify({
features: fts,
type: 'FeatureCollection'
});

fs.writeFileSync('isochrones.geojson', collection);

}
});

}

}
```

poi.geojson
```
{
"type": "FeatureCollection",
"name": "poi",
"crs": { "type": "name", "properties": { "name": "urn:ogc:def:crs:OGC:1.3:CRS84" } },
"features": [
{ "type": "Feature", "properties": { "stop_id": 6, "stop_name": "Jackson & Lotus", "stop_lat": 41.876513, "stop_lon": -87.761446 }, "geometry": { "type": "Point", "coordinates": [ -87.761446, 41.876513 ] } },
{ "type": "Feature", "properties": { "stop_id": 2, "stop_name": "5900 W Jackson", "stop_lat": 41.87706679, "stop_lon": -87.77131794 }, "geometry": { "type": "Point", "coordinates": [ -87.77131794, 41.87706679 ] } },
{ "type": "Feature", "properties": { "stop_id": 1, "stop_name": "Jackson & Austin Terminal", "stop_lat": 41.87632184, "stop_lon": -87.77410482000001 }, "geometry": { "type": "Point", "coordinates": [ -87.77410482, 41.87632184 ] } },
{ "type": "Feature", "properties": { "stop_id": 4, "stop_name": "5700 W Jackson", "stop_lat": 41.87702418, "stop_lon": -87.76745055000001 }, "geometry": { "type": "Point", "coordinates": [ -87.76745055, 41.87702418 ] } },
{ "type": "Feature", "properties": { "stop_id": 3, "stop_name": "Jackson & Menard", "stop_lat": 41.87695725, "stop_lon": -87.76975039 }, "geometry": { "type": "Point", "coordinates": [ -87.76975039, 41.87695725 ] } }
]
}
```

Start with the supplied index.js and isochrone.js, then run the example with five points and with the larger GeoJSON. Inspect how concurrent requests, batchSize, and error responses are handled before the durations access. Done means repeated and larger runs handle the response without the reported TypeError and produce the expected isochrones.geojson output.

Written by the indexing model from the issue text.