diff --git a/lib/database.js b/lib/database.js
index e3b1a65..5198f99 100644
--- a/lib/database.js
+++ b/lib/database.js
@@ -11,13 +11,38 @@ const COLLECTION_NAME = 'feedback';
 
 const { validateInitialResponse, validateTextComments } = require('./validation.js');
 
+let dbClient;
+
+/**
+ * @returns {Promise} - A promise which returns a mongo database connection
+ */
+const getDb = async () => {
+  if (!dbClient) {
+    dbClient = await mongoClient.connect(CONNECTION_STRING, {
+      useUnifiedTopology: true,
+    });
+  }
+  return dbClient.db(DB_NAME);
+};
+
+/**
+ * Close the mongodb connection.
+ * This function usually shouldn't be used by application code since we want to re-use connections.
+ * It is useful for closing database connections between tests.
+ */
+module.exports.closeConnection = () => {
+  if (!dbClient) {
+    return;
+  }
+  dbClient.close();
+};
+
 /**
  * @returns {Promise} - A promise which returns true for healthy connection, false for unhealthy.
  */
 module.exports.healthcheck = async () => {
   try {
-    const client = await mongoClient.connect(CONNECTION_STRING);
-    const db = client.db(DB_NAME);
+    const db = await getDb();
     const result = await db.admin().ping();
     return result.ok === 1;
   } catch (err) {
@@ -31,26 +56,21 @@ module.exports.healthcheck = async () => {
  * @returns {Promise} - A promise which resolves to a unique token
  */
 const insertOrUpdate = async (data) => {
-  const client = await mongoClient.connect(CONNECTION_STRING);
-  const db = client.db(DB_NAME);
+  const db = await getDb();
   const collection = db.collection(COLLECTION_NAME);
-  try {
-    if (data.token) {
-      const filter = { token: data.token };
-      const options = { upsert: true };
-      await collection.updateOne(filter, { $set: data }, options);
-      return data.token;
-    }
-
-    const token = uuid();
-    await collection.insertOne({
-      ...data,
-      token,
-    });
-    return token;
-  } finally {
-    client.close();
+  if (data.token) {
+    const filter = { token: data.token };
+    const options = { upsert: true };
+    await collection.updateOne(filter, { $set: data }, options);
+    return data.token;
   }
+
+  const token = uuid();
+  await collection.insertOne({
+    ...data,
+    token,
+  });
+  return token;
 };
 
 /**
diff --git a/lib/database.test.js b/lib/database.test.js
index 453094a..5ceec80 100644
--- a/lib/database.test.js
+++ b/lib/database.test.js
@@ -23,7 +23,11 @@ describe('database', () => {
   });
 
   afterAll(async () => {
+    // Close the connection used by tests to set up data
     await connection.close();
+
+    // Close the connection used by the application
+    await database.closeConnection();
   });
 
   it('inserts true answer into database', async () => {