diff --git a/bin/index.js b/bin/index.js
index 87b7314..2f122b3 100755
--- a/bin/index.js
+++ b/bin/index.js
@@ -32,6 +32,10 @@ var argv = yargs
     routes: {
       alias: 'r',
       description: 'Load routes file'
+    },
+    id: {
+      description: 'Set database id property (e.g. _id)',
+      default: 'id'
     }
   })
   .help('help').alias('help', 'h')
@@ -118,6 +122,10 @@ function start (object, filename) {
   }
 
   server.use(router)
+
+  // Custom id
+  router.db._.id = argv.id
+
   server.listen(port, argv.host)
 }
 
diff --git a/package.json b/package.json
index 1bb2738..74b4e2b 100644
--- a/package.json
+++ b/package.json
@@ -15,7 +15,7 @@
     "express": "^4.9.5",
     "got": "^1.2.2",
     "lodash": "^3.9.2",
-    "lowdb": "^0.9.0",
+    "lowdb": "^0.10.0",
     "method-override": "^2.1.2",
     "morgan": "^1.3.1",
     "node-uuid": "^1.4.2",
diff --git a/src/mixins.js b/src/mixins.js
new file mode 100644
index 0000000..b43b9e4
--- /dev/null
+++ b/src/mixins.js
@@ -0,0 +1,77 @@
+var uuid = require('node-uuid')
+var pluralize = require('pluralize')
+
+module.exports = {
+  getRemovable: getRemovable,
+  createId: createId,
+  deepQuery: deepQuery
+}
+
+// Returns document ids that have unsatisfied relations
+// Example: a comment that references a post that doesn't exist
+function getRemovable (db) {
+  var _ = this
+  var removable = []
+  _.each(db, function (coll, collName) {
+    _.each(coll, function (doc) {
+      _.each(doc, function (value, key) {
+        if (/Id$/.test(key)) {
+          var refName = pluralize.plural(key.slice(0, -2))
+          // Test if table exists
+          if (db[refName]) {
+            // Test if references is defined in table
+            var ref = _.getById(db[refName], value)
+            if (_.isUndefined(ref)) {
+              removable.push({name: collName, id: doc.id})
+            }
+          }
+        }
+      })
+    })
+  })
+
+  return removable
+}
+
+// Return incremented id or uuid
+// Used to override underscore-db's createId with utils.createId
+function createId (coll) {
+  var _ = this
+  var idProperty = _.__id()
+  if (_.isEmpty(coll)) {
+    return 1
+  } else {
+    var id = _.max(coll, function (doc) {
+      return doc[idProperty]
+    })[idProperty]
+
+    if (_.isFinite(id)) {
+      // Increment integer id
+      return ++id
+    } else {
+      // Generate string id
+      return uuid()
+    }
+  }
+}
+
+function deepQuery (value, q) {
+  var _ = this
+  if (value && q) {
+    if (_.isArray(value)) {
+      for (var i = 0; i < value.length; i++) {
+        if (deepQuery(value[i], q)) {
+          return true
+        }
+      }
+    } else if (_.isObject(value) && !_.isArray(value)) {
+      for (var k in value) {
+        if (deepQuery(value[k], q)) {
+          return true
+        }
+      }
+    } else if (value.toString().toLowerCase().indexOf(q) !== -1) {
+      return true
+    }
+  }
+}
diff --git a/src/router.js b/src/router.js
index 1b71942..5521180 100644
--- a/src/router.js
+++ b/src/router.js
@@ -6,6 +6,7 @@ var _db = require('underscore-db')
 var low = require('lowdb')
 var pluralize = require('pluralize')
 var utils = require('./utils')
+var mixins = require('./mixins')
 
 module.exports = function (source) {
   // Create router
@@ -26,11 +27,10 @@ module.exports = function (source) {
   }
 
   // Add underscore-db methods to db
-  db.mixin(_db)
+  db._.mixin(_db)
 
-  // Override underscore-db's createId with utils.createId
-  // utils.createId can generate incremental id or uuid
-  db.mixin({createId: utils.createId})
+  // Add specific mixins
+  db._.mixin(mixins)
 
   // Expose database
   router.db = db
@@ -86,7 +86,7 @@ module.exports = function (source) {
       array = db(req.params.resource).filter(function (obj) {
         for (var key in obj) {
           var value = obj[key]
-          if (utils.deepQuery(value, q)) {
+          if (db._.deepQuery(value, q)) {
             return true
           }
         }
@@ -226,7 +226,7 @@ module.exports = function (source) {
     db(req.params.resource).removeById(utils.toNative(req.params.id))
 
     // Remove dependents documents
-    var removable = utils.getRemovable(db.object)
+    var removable = db._.getRemovable(db.object)
 
     _.each(removable, function (item) {
       db(item.name).removeById(item.id)
diff --git a/src/utils.js b/src/utils.js
index 53a7811..397e2ff 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -1,6 +1,6 @@
-var _ = require('lodash')
-var uuid = require('node-uuid')
-var pluralize = require('pluralize')
+module.exports = {
+  toNative: toNative
+}
 
 // Turns string to native.
 // Example:
@@ -20,74 +20,3 @@ function toNative (value) {
   }
   return value
 }
-
-// Return incremented id or uuid
-function createId (coll) {
-  if (_.isEmpty(coll)) {
-    return 1
-  } else {
-    var id = _.max(coll, function (doc) {
-      return doc.id
-    }).id
-
-    if (_.isFinite(id)) {
-      // Increment integer id
-      return ++id
-    } else {
-      // Generate string id
-      return uuid()
-    }
-  }
-}
-
-// Returns document ids that have unsatisfied relations
-// Example: a comment that references a post that doesn't exist
-function getRemovable (db) {
-  var removable = []
-  _.each(db, function (coll, collName) {
-    _.each(coll, function (doc) {
-      _.each(doc, function (value, key) {
-        if (/Id$/.test(key)) {
-          var refName = pluralize.plural(key.slice(0, -2))
-          // Test if table exists
-          if (db[refName]) {
-            // Test if references is defined in table
-            var ref = _.findWhere(db[refName], {id: value})
-            if (_.isUndefined(ref)) {
-              removable.push({name: collName, id: doc.id})
-            }
-          }
-        }
-      })
-    })
-  })
-
-  return removable
-}
-
-function deepQuery (value, q) {
-  if (value && q) {
-    if (_.isArray(value)) {
-      for (var i = 0; i < value.length; i++) {
-        if (deepQuery(value[i], q)) {
-          return true
-        }
-      }
-    } else if (_.isObject(value) && !_.isArray(value)) {
-      for (var k in value) {
-        if (deepQuery(value[k], q)) {
-          return true
-        }
-      }
-    } else if (value.toString().toLowerCase().indexOf(q) !== -1) {
-      return true
-    }
-  }
-}
-
-module.exports = {
-  toNative: toNative,
-  createId: createId,
-  getRemovable: getRemovable,
-  deepQuery: deepQuery
-}
diff --git a/test/index.js b/test/index.js
index b7498a3..e793e8a 100644
--- a/test/index.js
+++ b/test/index.js
@@ -405,4 +405,26 @@ describe('Server', function () {
     })
 
   })
+
+  describe('router.db._.id', function (done) {
+
+    beforeEach(function () {
+      router.db.object = {
+        posts: [
+          { _id: 1 }
+        ]
+      }
+
+      router.db._.id = '_id'
+    })
+
+    it('should be possible to override id property', function (done) {
+      request(server)
+        .get('/posts/1')
+        .expect('Content-Type', /json/)
+        .expect(router.db.object.posts[0])
+        .expect(200, done)
+    })
+
+  })
 })
diff --git a/test/mixins.js b/test/mixins.js
new file mode 100644
index 0000000..88210fb
--- /dev/null
+++ b/test/mixins.js
@@ -0,0 +1,38 @@
+var assert = require('assert')
+var mixins = require('../src/mixins')
+var _ = require('lodash')
+var _db = require('underscore-db')
+
+/* global describe, it */
+
+describe('mixins', function () {
+
+  describe('getRemovable', function () {
+
+    it('should return removable documents', function () {
+
+      var db = {
+        posts: [
+          {id: 1, comment: 1}
+        ],
+        comments: [
+          {id: 1, postId: 1},
+          // Comments below references a post that doesn't exist
+          {id: 2, postId: 2},
+          {id: 3, postId: 2}
+        ]
+      }
+
+      var expected = [
+        {name: 'comments', id: 2},
+        {name: 'comments', id: 3}
+      ]
+
+      _.mixin(_db)
+      _.mixin(mixins)
+
+      assert.deepEqual(_.getRemovable(db), expected)
+
+    })
+  })
+})
diff --git a/test/utils.js b/test/utils.js
index 0e7bfdd..13c7d0a 100644
--- a/test/utils.js
+++ b/test/utils.js
@@ -5,32 +5,6 @@ var utils = require('../src/utils')
 
 describe('utils', function () {
 
-  describe('getRemovable', function () {
-
-    it('should return removable documents', function () {
-
-      var db = {
-        posts: [
-          {id: 1, comment: 1}
-        ],
-        comments: [
-          {id: 1, postId: 1},
-          // Comments below references a post that doesn't exist
-          {id: 2, postId: 2},
-          {id: 3, postId: 2}
-        ]
-      }
-
-      var expected = [
-        {name: 'comments', id: 2},
-        {name: 'comments', id: 3}
-      ]
-
-      assert.deepEqual(utils.getRemovable(db), expected)
-
-    })
-  })
-
   describe('toNative', function () {
 
     it('should convert string to native type', function () {