diff --git a/Changelog.md b/Changelog.md
index 2e719f8..ea6be8a 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -5,6 +5,10 @@ This is the changelog for the air quality web interface and its associated HTTP
  - `[Code]` refers to internal changes to the code that have no direct impact on the web interface or the HTTP API, but are significant enough to warrant note.
  - `[Docs]` refers to changes to the [documentation](https://aq.connectedhumber.org/__nightdocs/00-Welcome.html).
 
+## v0.11.1 - 22nd June 2019
+ - Drastically improve the performance of the backend SQL queries that power the heatmap and device graphs by over 35x!
+     - For users of the HTTP API, said queries are `fetch-data` and `device-data`.
+
 ## v0.11 - 21st June 2019
  - [API] Add new [`list-devices-near`](https://aq.connectedhumber.org/__nightdocs/05-API-Docs.html#list-devices-near) action.
  - [API] Clarified that clients MUST ignore properties returned by the API that they do not understand.
diff --git a/lib/SBRL/Generators.php b/lib/SBRL/Generators.php
index 195dfa3..4e65706 100644
--- a/lib/SBRL/Generators.php
+++ b/lib/SBRL/Generators.php
@@ -4,6 +4,12 @@ namespace SBRL;
 
 class Generators {
 	
+	/**
+	 * Generates a cryptographically secure random id, as a hex value.
+	 * FUTURE: Improve this to return a safe base64 to reduce length.
+	 * @param	int	$length	The desired length of id.
+	 * @return	string	The generated id.
+	 */
 	public static function crypto_secure_id(int $length = 64) { // 64 = 32
         $length = ($length < 4) ? 4 : $length;
         return bin2hex(random_bytes(($length-($length%2))/2));
diff --git a/logic/ApiResponseSender.php b/logic/ApiResponseSender.php
index bd92fc9..4b16524 100644
--- a/logic/ApiResponseSender.php
+++ b/logic/ApiResponseSender.php
@@ -7,11 +7,20 @@ namespace AirQuality;
  */
 class ApiResponseSender
 {
-	
+	/**
+	 * Creates a new ApiResponseSender.
+	 */
 	function __construct() {
 		
 	}
 	
+	/**
+	 * Sends a plain-text error message.
+	 * @param	int		$code			The HTTP status code to send.
+	 * @param	string	$message		The plain-text message to send.
+	 * @param	array	$extra_headers	Any extra headers to return, in the format [["header", "value"], ["header", "value"], .....]
+	 * @return	void
+	 */
 	public function send_error_plain($code, $message, $extra_headers = []) {
 		http_response_code($code);
 		header("content-type: text/plain");
diff --git a/logic/Constants.php b/logic/Constants.php
new file mode 100644
index 0000000..598baa7
--- /dev/null
+++ b/logic/Constants.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace AirQuality;
+
+/**
+ * Holds various constant value.
+ */
+class Constants 
+{
+	/**
+	 * The DateTime->format() string for passing DateTimes to MariaDB.
+	 * Note that if you don't use thsi format and use the ISO standard instead, it will silently complain at you, taking absolutely _ages_ over doing so.
+	 * @var string
+	 */
+	const DATETIME_FORMAT_SQL = "Y-m-d H:i:s";
+	
+	/**
+	 * You should never instantiate an instance of this class!
+	 */
+	private function __construct() {  }
+}
diff --git a/logic/Database.php b/logic/Database.php
index 699decb..7ffd1e4 100644
--- a/logic/Database.php
+++ b/logic/Database.php
@@ -56,8 +56,10 @@ class Database
 		// Replace tabs with spaces for debugging purposes
 		$sql = str_replace("\t", "    ", $sql);
 		
-		if($this->settings->get("env.mode") == "development")
+		if($this->settings->get("env.mode") == "development") {
+			// error_log("[Database/SQL]" . var_export($variables, true));
 			error_log("[Database/SQL] $sql");
+		}
 		
 		// FUTURE: Optionally cache prepared statements?
 		$statement = $this->connection->prepare($sql);
diff --git a/logic/Repositories/MariaDBMeasurementDataRepository.php b/logic/Repositories/MariaDBMeasurementDataRepository.php
index 4188927..54925e4 100644
--- a/logic/Repositories/MariaDBMeasurementDataRepository.php
+++ b/logic/Repositories/MariaDBMeasurementDataRepository.php
@@ -2,6 +2,7 @@
 
 namespace AirQuality\Repositories;
 
+use \AirQuality\Constants;
 use \AirQuality\Database;
 use \SBRL\TomlConfig;
 
@@ -97,8 +98,8 @@ class MariaDBMeasurementDataRepository implements IMeasurementDataRepository {
 				", [
 				"reading_type" => $type_id,
 				// The database likes strings, not PHP DateTime() instances
-				"start_datetime" => $start_datetime->format(\DateTime::ISO8601),
-				"end_datetime" => $end_datetime->format(\DateTime::ISO8601),
+				"start_datetime" => $start_datetime->format(Constants::DATETIME_FORMAT_SQL),
+				"end_datetime" => $end_datetime->format(Constants::DATETIME_FORMAT_SQL),
 			]
 		)->fetchAll();
 	}
@@ -138,8 +139,8 @@ class MariaDBMeasurementDataRepository implements IMeasurementDataRepository {
 			GROUP BY CEIL(UNIX_TIMESTAMP({$s("table_name_metadata")}.{$s("column_metadata_datetime")}) / :average_seconds);", [
 				"device_id" => $device_id,
 				"reading_type" => $type_id,
-				"start_datetime" => $start->format(\DateTime::ISO8601),
-				"end_datetime" => $end->format(\DateTime::ISO8601),
+				"start_datetime" => $start->format(Constants::DATETIME_FORMAT_SQL),
+				"end_datetime" => $end->format(Constants::DATETIME_FORMAT_SQL),
 				"average_seconds" => $average_seconds
 			]
 		)->fetchAll();
diff --git a/version b/version
index 5416288..4f7638f 100644
--- a/version
+++ b/version
@@ -1 +1 @@
-v0.11
+v0.11.1