diff --git a/lib/datastore.js b/lib/datastore.js
index 491a3f2..9dd255c 100755
--- a/lib/datastore.js
+++ b/lib/datastore.js
@@ -1,4 +1,5 @@
 const { EventEmitter } = require('events')
+const { callbackify } = require('util')
 const async = require('async')
 const Cursor = require('./cursor.js')
 const customUtils = require('./customUtils.js')
@@ -267,26 +268,61 @@ class Datastore extends EventEmitter {
    * @param {Boolean} dontExpireStaleDocs Optional, defaults to false, if true don't remove stale docs. Useful for the remove function which shouldn't be impacted by expirations
    * @param {Function} callback Signature err, candidates
    */
-  async getCandidates (query, dontExpireStaleDocs, callback) {
-    const validDocs = []
-
+  getCandidates (query, dontExpireStaleDocs, callback) {
     if (typeof dontExpireStaleDocs === 'function') {
       callback = dontExpireStaleDocs
       dontExpireStaleDocs = false
     }
 
-    try {
+    callbackify(this.getCandidatesAsync.bind(this))(query, dontExpireStaleDocs, callback)
+  }
+
+  async getCandidatesAsync (query, dontExpireStaleDocs = false) {
+    const indexNames = Object.keys(this.indexes)
+    const validDocs = []
+
+    const _getCandidates = query => {
       // STEP 1: get candidates list by checking indexes from most to least frequent usecase
-      const docs = this._getCandidates(query)
-      // STEP 2: remove all expired documents
+      // For a basic match
+      let usableQuery
+      usableQuery = Object.entries(query)
+        .filter(([k, v]) =>
+          !!(typeof v === 'string' || typeof v === 'number' || typeof v === 'boolean' || isDate(v) || v === null) &&
+          indexNames.includes(k)
+        )
+        .pop()
+      if (usableQuery) return this.indexes[usableQuery[0]].getMatching(usableQuery[1])
+      // For a $in match
+      usableQuery = Object.entries(query)
+        .filter(([k, v]) =>
+          !!(query[k] && Object.prototype.hasOwnProperty.call(query[k], '$in')) &&
+          indexNames.includes(k)
+        )
+        .pop()
+      if (usableQuery) return this.indexes[usableQuery[0]].getMatching(usableQuery[1].$in)
+      // For a comparison match
+      usableQuery = Object.entries(query)
+        .filter(([k, v]) =>
+          !!(query[k] && (Object.prototype.hasOwnProperty.call(query[k], '$lt') || Object.prototype.hasOwnProperty.call(query[k], '$lte') || Object.prototype.hasOwnProperty.call(query[k], '$gt') || Object.prototype.hasOwnProperty.call(query[k], '$gte'))) &&
+          indexNames.includes(k)
+        )
+        .pop()
+      if (usableQuery) return this.indexes[usableQuery[0]].getBetweenBounds(usableQuery[1])
+      // By default, return all the DB data
+      return this.getAllData()
+    }
+
+    // STEP 1: get candidates list by checking indexes from most to least frequent usecase
+    const docs = _getCandidates(query)
+    // STEP 2: remove all expired documents
       if (!dontExpireStaleDocs) {
-        const expiredDocsIds = []
-        const ttlIndexesFieldNames = Object.keys(this.ttlIndexes)
+      const expiredDocsIds = []
+      const ttlIndexesFieldNames = Object.keys(this.ttlIndexes)
 
-        docs.forEach(doc => {
+      docs.forEach(doc => {
           if (ttlIndexesFieldNames.every(i => !(doc[i] !== undefined && isDate(doc[i]) && Date.now() > doc[i].getTime() + this.ttlIndexes[i] * 1000))) validDocs.push(doc)
-          else expiredDocsIds.push(doc._id)
-        })
+        else expiredDocsIds.push(doc._id)
+      })
         for (const _id of expiredDocsIds) {
           await new Promise((resolve, reject) => {
             this._remove({ _id: _id }, {}, err => {
@@ -294,14 +330,9 @@ class Datastore extends EventEmitter {
               return resolve()
             })
           })
-        }
-      } else validDocs.push(...docs)
-    } catch (error) {
-      if (typeof callback === 'function') callback(error, null)
-      else throw error
-    }
-    if (typeof callback === 'function') callback(null, validDocs)
-    else return validDocs
+      }
+    } else validDocs.push(...docs)
+    return validDocs
   }
 
   /**
@@ -509,92 +540,90 @@ class Datastore extends EventEmitter {
       options = {}
     }
     const callback = cb || (() => {})
+
+    const _callback = (err, res = {}) => {
+      callback(err, res.numAffected, res.affectedDocuments, res.upsert)
+    }
+    callbackify(this._updateAsync.bind(this))(query, updateQuery, options, _callback)
+  }
+
+  async _updateAsync (query, updateQuery, options = {}) {
     const multi = options.multi !== undefined ? options.multi : false
     const upsert = options.upsert !== undefined ? options.upsert : false
 
-    async.waterfall([
-      cb => { // If upsert option is set, check whether we need to insert the doc
-        if (!upsert) return cb()
+    // If upsert option is set, check whether we need to insert the doc
+    if (upsert) {
+      // Need to use an internal function not tied to the executor to avoid deadlock
+      const cursor = new Cursor(this, query)
 
-        // Need to use an internal function not tied to the executor to avoid deadlock
-        const cursor = new Cursor(this, query)
+      const docs = await new Promise((resolve, reject) => {
         cursor.limit(1)._exec((err, docs) => {
-          if (err) return callback(err)
-          if (docs.length === 1) return cb()
-          else {
-            let toBeInserted
-
-            try {
-              model.checkObject(updateQuery)
-              // updateQuery is a simple object with no modifier, use it as the document to insert
-              toBeInserted = updateQuery
-            } catch (e) {
-              // updateQuery contains modifiers, use the find query as the base,
-              // strip it from all operators and update it according to updateQuery
-              try {
-                toBeInserted = model.modify(model.deepCopy(query, true), updateQuery)
-              } catch (err) {
-                return callback(err)
-              }
-            }
-
-            return this._insert(toBeInserted, (err, newDoc) => {
-              if (err) return callback(err)
-              return callback(null, 1, newDoc, true)
-            })
-          }
+          if (err) reject(err)
+          else resolve(docs)
         })
-      },
-      () => { // Perform the update
-        let numReplaced = 0
-        let modifiedDoc
-        const modifications = []
-        let createdAt
-
-        this.getCandidates(query, (err, candidates) => {
-          if (err) return callback(err)
-
-          // Preparing update (if an error is thrown here neither the datafile nor
-          // the in-memory indexes are affected)
-          try {
-            for (const candidate of candidates) {
-              if (model.match(candidate, query) && (multi || numReplaced === 0)) {
-                numReplaced += 1
-                if (this.timestampData) { createdAt = candidate.createdAt }
-                modifiedDoc = model.modify(candidate, updateQuery)
-                if (this.timestampData) {
-                  modifiedDoc.createdAt = createdAt
-                  modifiedDoc.updatedAt = new Date()
-                }
-                modifications.push({ oldDoc: candidate, newDoc: modifiedDoc })
-              }
-            }
-          } catch (err) {
-            return callback(err)
-          }
+      })
 
-          // Change the docs in memory
-          try {
-            this.updateIndexes(modifications)
-          } catch (err) {
-            return callback(err)
-          }
+      if (docs.length !== 1) {
+        let toBeInserted
+
+        try {
+          model.checkObject(updateQuery)
+          // updateQuery is a simple object with no modifier, use it as the document to insert
+          toBeInserted = updateQuery
+        } catch (e) {
+          // updateQuery contains modifiers, use the find query as the base,
+          // strip it from all operators and update it according to updateQuery
+          toBeInserted = model.modify(model.deepCopy(query, true), updateQuery)
+        }
 
-          // Update the datafile
-          const updatedDocs = modifications.map(x => x.newDoc)
-          this.persistence.persistNewState(updatedDocs, err => {
-            if (err) return callback(err)
-            if (!options.returnUpdatedDocs) {
-              return callback(null, numReplaced)
-            } else {
-              let updatedDocsDC = []
-              updatedDocs.forEach(doc => { updatedDocsDC.push(model.deepCopy(doc)) })
-              if (!multi) updatedDocsDC = updatedDocsDC[0]
-              return callback(null, numReplaced, updatedDocsDC)
-            }
+        return new Promise((resolve, reject) => {
+          this._insert(toBeInserted, (err, newDoc) => {
+            if (err) return reject(err)
+            return resolve({ numAffected: 1, affectedDocuments: newDoc, upsert: true })
           })
         })
-      }])
+      }
+    }
+    // Perform the update
+    let numReplaced = 0
+    let modifiedDoc
+    const modifications = []
+    let createdAt
+
+    const candidates = await this.getCandidatesAsync(query)
+    // Preparing update (if an error is thrown here neither the datafile nor
+    // the in-memory indexes are affected)
+    for (const candidate of candidates) {
+      if (model.match(candidate, query) && (multi || numReplaced === 0)) {
+        numReplaced += 1
+        if (this.timestampData) { createdAt = candidate.createdAt }
+        modifiedDoc = model.modify(candidate, updateQuery)
+        if (this.timestampData) {
+          modifiedDoc.createdAt = createdAt
+          modifiedDoc.updatedAt = new Date()
+        }
+        modifications.push({ oldDoc: candidate, newDoc: modifiedDoc })
+      }
+    }
+
+    // Change the docs in memory
+    this.updateIndexes(modifications)
+
+    // Update the datafile
+    const updatedDocs = modifications.map(x => x.newDoc)
+    await new Promise((resolve, reject) => {
+      this.persistence.persistNewState(updatedDocs, err => {
+        if (err) return reject(err)
+        else resolve()
+      })
+    })
+    if (!options.returnUpdatedDocs) return { numAffected: numReplaced }
+    else {
+      let updatedDocsDC = []
+      updatedDocs.forEach(doc => { updatedDocsDC.push(model.deepCopy(doc)) })
+      if (!multi) updatedDocsDC = updatedDocsDC[0]
+      return { numAffected: numReplaced, affectedDocuments: updatedDocsDC }
+    }
   }
 
   update () {