This is a simple API created using Node.js, restify and mongoose with MongoDB.

app.js

var restify = require('restify'),
    mongoose = require('mongoose');
var server = restify.createServer({
    name: 'mongo-api'
})
server.listen(7000, function () {
    console.log('%s listening at %s', server.name, server.url)
})

db = mongoose.connect("mongodb://localhost/example-api");
var Schema = mongoose.Schema,
    ObjectId = Schema.ObjectID;

var User = new Schema({
    email: {
        type: String,
        required: true,
        trim: true
    },
    fname: {
        type: String,
        required: false,
        trim: true
    },
    lname: {
        type: String,
        required: false,
        trim: true
    },

});

var User = mongoose.model('User', User);

server
    .use(restify.fullResponse())
    .use(restify.bodyParser())

server.get('/user', function (req, res, next) {
    User.find({}, function (error, users) {
        res.send(users)
    })
})

server.post('/user', function (req, res, next) {
    if (req.params.email === undefined) {
        return next(new restify.InvalidArgumentError('Email must be supplied'))
    }
    var userData = {
        email: req.params.email,
        fname: req.params.fname,
        lname: req.params.lname
    }
    var user = new User(userData);
    user.save(function (error, data) {
        if (error) {
            return next(new restify.InvalidArgumentError(JSON.stringify(error.errors)))
        }
        else {
            res.json(data);
        }
        res.send(201, user)
    })
})

server.get('/user/:id', function (req, res, next) {
    User.findOne({
        _id: req.params.id
    }, function (error, user) {
        if (error) return next(new restify.InvalidArgumentError(JSON.stringify(error.errors)))

        if (user) {
            res.send(user)
        }
        else {
            res.send(404)
        }
    })
})

server.put('/user/:id', function (req, res, next) {
    if (req.params.email === undefined) {
        return next(new restify.InvalidArgumentError('Email must be supplied'))
    }
    var userData = {
        email: req.params.email,
        fname: req.params.fname,
        lname: req.params.lname
    }
    User.update({
        _id: req.params.id
    }, userData, {
        multi: false
    }, function (error, user) {
        if (error) return next(new restify.InvalidArgumentError(JSON.stringify(error.errors)))
        res.send()
    })
})

server.del('/user/:id', function (req, res, next) {
    User.remove({
        _id: req.params.id
    }, function (error, user) {
        if (error) return next(new restify.InvalidArgumentError(JSON.stringify(error.errors)))

        res.send()
    })
})