Dgraph execution failed because 429 Too Many Requests

I am using dgraph standalone setup & I am testing my node back-end that is connected to dgraph standalone with wrk and I am getting this response from dgraph: Dgraph query failed because Dgraph execution failed because 429 Too Many Requests. Please throttle your requests . So clearly the bottleneck in here is dgraph itself. Why is this happening & How to improve or solve this problem?
I am using this command: wrk -t1 -c1 -d1s <my node app api endpoint> .
-t stands for threads and -c stands for number of connections and -d for duration.

Node: There is only one input in database.


type User {
  id: ID!
  name: String
  username: String! @id
Running 2s test @ http://localhost:3003/api/users
  2 threads and 2 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     4.58ms    1.10ms  12.67ms   81.67%
    Req/Sec   219.52     17.62   250.00     65.00%
  875 requests in 2.00s, 231.57KB read
  Non-2xx or 3xx responses: 875
Requests/sec:    436.92
Transfer/sec:    115.63KB