diff --git a/src/database/mongo/main.js b/src/database/mongo/main.js
index 77f1f1409c..aa5892389b 100644
--- a/src/database/mongo/main.js
+++ b/src/database/mongo/main.js
@@ -24,12 +24,8 @@ module.exports = function (module) {
 				_key: { $in: key },
 			}, { _id: 0, _key: 1 }).toArray();
 
-			const map = Object.create(null);
-			data.forEach((item) => {
-				map[item._key] = true;
-			});
-
-			return key.map(key => !!map[key]);
+			const foundKeys = new Set(data.map(item => item._key));
+			return key.map(key => foundKeys.has(key));
 		}
 
 		const item = await module.client.collection('objects').findOne({
@@ -76,7 +72,9 @@ module.exports = function (module) {
 			return;
 		}
 
-		const objectData = await module.client.collection('objects').findOne({ _key: key }, { projection: { _id: 0 } });
+		const objectData = await module.client.collection('objects').findOne(
+			{ _key: key }, { projection: { _id: 0 } }
+		);
 
 		// fallback to old field name 'value' for backwards compatibility #6340
 		let value = null;
@@ -100,12 +98,12 @@ module.exports = function (module) {
 			{ projection: { _id: 0 } }
 		).toArray();
 
-		const map = {};
+		const map = Object.create(null);
 		data.forEach((d) => {
 			map[d._key] = d.data;
 		});
 
-		return keys.map(k => (map.hasOwnProperty(k) ? map[k] : null));
+		return keys.map(k => map[k] !== undefined ? map[k] : null);
 	};
 
 	module.set = async function (key, value) {
diff --git a/src/database/mongo/sets.js b/src/database/mongo/sets.js
index 66b4baebab..32e81f37b1 100644
--- a/src/database/mongo/sets.js
+++ b/src/database/mongo/sets.js
@@ -128,7 +128,7 @@ module.exports = function (module) {
 		const item = await module.client.collection('objects').findOne({
 			_key: key, members: value,
 		}, {
-			projection: { _id: 0, _key: 1},
+			projection: { _id: 0, _key: 1 },
 		});
 
 		return item !== null && item !== undefined;
@@ -177,12 +177,8 @@ module.exports = function (module) {
 			projection: { _id: 0, _key: 1 },
 		}).toArray();
 
-		const map = {};
-		result.forEach((item) => {
-			map[item._key] = true;
-		});
-
-		return sets.map(set => !!map[set]);
+		const foundMembers = new Set(result.map(item => item._key));
+		return sets.map(set => foundMembers.has(set));
 	};
 
 	module.getSetMembers = async function (key) {
@@ -208,7 +204,7 @@ module.exports = function (module) {
 			projection: { _id: 0 },
 		}).toArray();
 
-		const sets = {};
+		const sets = Object.create(null);
 		data.forEach((set) => {
 			sets[set._key] = set.members || [];
 		});
diff --git a/src/database/mongo/sorted.js b/src/database/mongo/sorted.js
index 9940cf2677..b5de27ef6b 100644
--- a/src/database/mongo/sorted.js
+++ b/src/database/mongo/sorted.js
@@ -271,7 +271,10 @@ module.exports = function (module) {
 			return null;
 		}
 		value = helpers.valueToString(value);
-		const result = await module.client.collection('objects').findOne({ _key: key, value: value }, { projection: { _id: 0, _key: 0, value: 0 } });
+		const result = await module.client.collection('objects').findOne(
+			{ _key: key, value: value },
+			{ projection: { _id: 0, _key: 0, value: 0 } }
+		);
 		return result ? result.score : null;
 	};
 
@@ -280,15 +283,15 @@ module.exports = function (module) {
 			return [];
 		}
 		value = helpers.valueToString(value);
-		const result = await module.client.collection('objects').find({ _key: { $in: keys }, value: value }, { projection: { _id: 0, value: 0 } }).toArray();
-		const map = {};
+		const result = await module.client.collection('objects').find(
+			{ _key: { $in: keys }, value: value },
+			{ projection: { _id: 0, value: 0 } }
+		).toArray();
+		const scoreMap = Object.create(null);
 		result.forEach((item) => {
-			if (item) {
-				map[item._key] = item;
-			}
+			scoreMap[item._key] = item.score;
 		});
-
-		return keys.map(key => (map[key] ? map[key].score : null));
+		return keys.map(key => (scoreMap[key] !== undefined ? scoreMap[key] : null));
 	};
 
 	module.sortedSetScores = async function (key, values) {
@@ -299,13 +302,14 @@ module.exports = function (module) {
 			return [];
 		}
 		values = values.map(helpers.valueToString);
-		const result = await module.client.collection('objects').find({ _key: key, value: { $in: values } }, { projection: { _id: 0, _key: 0 } }).toArray();
+		const result = await module.client.collection('objects').find(
+			{ _key: key, value: { $in: values } },
+			{ projection: { _id: 0, _key: 0 } }
+		).toArray();
 
-		const valueToScore = {};
+		const valueToScore = Object.create(null);
 		result.forEach((item) => {
-			if (item) {
-				valueToScore[item.value] = item.score;
-			}
+			valueToScore[item.value] = item.score;
 		});
 
 		return values.map(v => (utils.isNumber(valueToScore[v]) ? valueToScore[v] : null));
@@ -338,14 +342,8 @@ module.exports = function (module) {
 			projection: { _id: 0, value: 1 },
 		}).toArray();
 
-		const isMember = {};
-		results.forEach((item) => {
-			if (item) {
-				isMember[item.value] = true;
-			}
-		});
-
-		return values.map(value => !!isMember[value]);
+		const foundMembers = new Set(results.map(item => item.value));
+		return values.map(value => foundMembers.has(value));
 	};
 
 	module.isMemberOfSortedSets = async function (keys, value) {
@@ -359,14 +357,8 @@ module.exports = function (module) {
 			projection: { _id: 0, _key: 1, value: 1 },
 		}).toArray();
 
-		const isMember = {};
-		results.forEach((item) => {
-			if (item) {
-				isMember[item._key] = true;
-			}
-		});
-
-		return keys.map(key => !!isMember[key]);
+		const keysWithMember = new Set(results.map(item => item._key));
+		return keys.map(key => keysWithMember.has(key));
 	};
 
 	module.getSortedSetMembers = async function (key) {
@@ -411,7 +403,7 @@ module.exports = function (module) {
 				data.map(item => item.value),
 			];
 		}
-		const sets = {};
+		const sets = Object.create(null);
 		data.forEach((item) => {
 			sets[item._key] = sets[item._key] || [];
 			if (withScores) {
diff --git a/src/database/mongo/sorted/remove.js b/src/database/mongo/sorted/remove.js
index d6bf96fa7e..80545d56fe 100644
--- a/src/database/mongo/sorted/remove.js
+++ b/src/database/mongo/sorted/remove.js
@@ -56,8 +56,8 @@ module.exports = function (module) {
 		if (!Array.isArray(data) || !data.length) {
 			return;
 		}
-		const bulk = module.client.collection('objects').initializeUnorderedBulkOp();
-		data.forEach(item => bulk.find({ _key: item[0], value: String(item[1]) }).delete());
-		await bulk.execute();
+		await module.client.collection('objects').deleteMany({
+			$or: data.map(([key, value]) => ({ _key: key, value: String(value) })),
+		});
 	};
 };
diff --git a/test/database/keys.js b/test/database/keys.js
index 673d083f98..84a3a7d495 100644
--- a/test/database/keys.js
+++ b/test/database/keys.js
@@ -44,6 +44,12 @@ describe('Key methods', () => {
 		assert.deepStrictEqual(await db.mget(null), []);
 	});
 
+	it('should return 0 if value of key is 0', async () => {
+		await db.set('zeroKey', 0);
+		const value = await db.mget(['zeroKey']);
+		assert.strictEqual(value[0], 0);
+	});
+
 	it('should return true if key exist', (done) => {
 		db.exists('testKey', function (err, exists) {
 			assert.ifError(err);