express.js and socket.io push api

gistfile1.js

var express = require('express');
var hbs = require('express3-handlebars');
var bodyParser = require('body-parser');
var logger = require('morgan');
var moment = require('moment');
var pg = require('pg');

var port = 3333;
var app = express();

var env = process.env.NODE_ENV || 'development'

if (env == 'development') {
  connectionString = "postgres://username@localhost/dev_database"
} else {
   connectionString = "postgres://username@localhost/production_database"
}

client = new pg.Client(connectionString);
client.connect();

app.use(logger());
app.use(bodyParser());
app.set('views', __dirname + '/views'); 
app.set('view engine', 'handlebars');
app.engine('handlebars', hbs({defaultLayout: app.get('views') + '/layouts/index'}));

var last_day_query = "select extract(epoch from date_trunc('minute', created_at)) as created_at, avg(temperature) as temperature,  " +
         "avg(humidity) as humidity " +
           "from readings " +
           "where created_at between " +
           "(CURRENT_TIMESTAMP AT TIME ZONE 'UTC' - INTERVAL '1 day') " +
           "and " +
           "(CURRENT_TIMESTAMP AT TIME ZONE 'UTC') " +
           "group by date_trunc('minute', created_at) " +
           "order by date_trunc('minute', created_at) " +
           "limit 1000; ";


var last_hour_query = "select extract(epoch from created_at) as created_at, temperature, humidity from " +
    "readings " +
    "where created_at between " + 
    "(CURRENT_TIMESTAMP AT TIME ZONE 'UTC' - INTERVAL '1 hour') " +
    "and " + 
    "(CURRENT_TIMESTAMP AT TIME ZONE 'UTC') limit 1000;";

    var last_year_query = "select extract(epoch from date_trunc('minute', created_at)) as created_at, avg(temperature) as temperature,  " +
    "avg(humidity) as humidity " +
    "from readings " +
    "where created_at between  " +
    "(CURRENT_TIMESTAMP AT TIME ZONE 'UTC' - INTERVAL '1 year') " +
    "and " +
    "(CURRENT_TIMESTAMP AT TIME ZONE 'UTC')  " +
    "group by date_trunc('minute', created_at)  " +
    "order by date_trunc('minute', created_at) asc";



var server = app.listen(port, function () {
  console.log('Listening on port %d', server.address().port);
});

var io = require('socket.io').listen(server);

app.get('/', function (req, res) {
  query = client.query('SELECT temperature, humidity, created_at from readings order by created_at desc limit 1');
  query.on('row', function(result) {
    result.temperature = parseFloat(result.temperature).toFixed(1);
    result.humidity = parseFloat(result.humidity).toFixed(1);
    result.last_refresh = result.created_at.toISOString();
    console.log(result.last_refresh);
    res.render('home', result);
  });
});

app.post('/reading', function (req, res) {
  reading = req.body
  client.query('INSERT INTO readings(id, temperature, humidity, created_at, updated_at) values ($1, $2, $3, $4, $5)',[reading.id, reading.temperature, reading.humidity, reading.created_at, moment.utc()]);
  reading.temperature = parseFloat(reading.temperature).toFixed(1);
  reading.humidity = parseFloat(reading.humidity).toFixed(1);
  reading.last_refresh = reading.created_at;
  io.sockets.emit('reading', reading);
  res.send(200);
});

app.get('/readings', function (req, res) {

  var qry = client.query(last_year_query);

  qry.on('row', function (row, result) {
    result.addRow(row);
  });

  qry.on('end', function(result) {
    res.json(result.rows);    
  });
});