diff --git a/build.sbt b/build.sbt
index c9d5e50..01eeee4 100644
--- a/build.sbt
+++ b/build.sbt
@@ -15,7 +15,7 @@ lazy val root = (project in file(".")).settings(
   libraryDependencies += "org.json4s" % "json4s-jackson_2.13" % "3.6.11"
 )
 
-unmanagedResourceDirectories in Compile += { baseDirectory.value / "lib" }
+Compile / unmanagedResourceDirectories += { baseDirectory.value / "lib" }
 scalacOptions ++= List(
   "-Yrangepos",
   "-Ywarn-unused",
@@ -23,8 +23,8 @@ scalacOptions ++= List(
 )
 javacOptions += "-g:none"
 compileOrder := CompileOrder.JavaThenScala
-mainClass in assembly := Some("lc.LCFramework")
-mainClass in (Compile, run) := Some("lc.LCFramework")
-assemblyJarName in assembly := "LibreCaptcha.jar"
+assembly / mainClass := Some("lc.LCFramework")
+Compile / run / mainClass := Some("lc.LCFramework")
+assembly / assemblyJarName  := "LibreCaptcha.jar"
 
-fork in run := true
+run / fork := true
diff --git a/project/build.properties b/project/build.properties
index dbae93b..e67343a 100644
--- a/project/build.properties
+++ b/project/build.properties
@@ -1 +1 @@
-sbt.version=1.4.9
+sbt.version=1.5.0
diff --git a/src/main/scala/lc/core/captcha.scala b/src/main/scala/lc/core/captcha.scala
index 34cda2f..4a04dc7 100644
--- a/src/main/scala/lc/core/captcha.scala
+++ b/src/main/scala/lc/core/captcha.scala
@@ -42,7 +42,7 @@ object Captcha {
     val token = if (rs.next()) {
       rs.getInt("token")
     }
-    println("Added new challenge: " + token.toString)
+    // println("Added new challenge: " + token.toString)
     token.asInstanceOf[Int]
   }
 
diff --git a/src/main/scala/lc/database/statements.scala b/src/main/scala/lc/database/statements.scala
index 1439b56..d23d6e2 100644
--- a/src/main/scala/lc/database/statements.scala
+++ b/src/main/scala/lc/database/statements.scala
@@ -4,7 +4,7 @@ import lc.database.DBConn
 import java.sql.Statement
 import java.sql.PreparedStatement
 
-class Statements(dbConn: DBConn) {
+class Statements(dbConn: DBConn, maxAttempts: Int) {
 
   private val stmt = dbConn.getStatement()
 
@@ -71,13 +71,14 @@ class Statements(dbConn: DBConn) {
   )
 
   val tokenPstmt: PreparedStatement = dbConn.con.prepareStatement(
-    "SELECT token " +
-      "FROM challenge " +
-      "WHERE attempted < 10 AND " +
-      "contentLevel = ? AND " +
-      "contentType = ? AND " +
-      "contentInput = ? " +
-      "ORDER BY RAND() LIMIT 1"
+    s"""
+      SELECT token
+        FROM challenge
+        WHERE attempted < $maxAttempts AND
+        contentLevel = ? AND
+        contentType = ? AND
+        contentInput = ?
+        ORDER BY RAND() LIMIT 1"""
   )
 
   val deleteAnswerPstmt: PreparedStatement = dbConn.con.prepareStatement(
@@ -85,9 +86,9 @@ class Statements(dbConn: DBConn) {
   )
 
   val challengeGCPstmt: PreparedStatement = dbConn.con.prepareStatement(
-    "DELETE FROM challenge " +
-      "WHERE attempted >= 10 AND " +
-      "token NOT IN (SELECT token FROM mapId)"
+    s"""DELETE FROM challenge
+      WHERE attempted >= $maxAttempts AND
+      token NOT IN (SELECT token FROM mapId)"""
   )
 
   val mapIdGCPstmt: PreparedStatement = dbConn.con.prepareStatement(
@@ -109,6 +110,14 @@ class Statements(dbConn: DBConn) {
 }
 
 object Statements {
+  /* Note: h2 documentation recommends using a separate DB connection per thread
+     But in practice, as of version 1.4.200, multiple connections occassionally shows error on the console of the form
+     ```
+     org.h2.jdbc.JdbcSQLNonTransientException: General error: "java.lang.NullPointerException"; SQL statement:
+     SELECT image FROM challenge c, mapId m WHERE c.token=m.token AND m.uuid = ? [50000-200]
+     ```
+     */
   private val dbConn: DBConn = new DBConn()
-  val tlStmts: ThreadLocal[Statements] = ThreadLocal.withInitial(() => new Statements(dbConn))
+  private val maxAttempts = 10
+  val tlStmts: ThreadLocal[Statements] = ThreadLocal.withInitial(() => new Statements(dbConn, maxAttempts))
 }
diff --git a/src/main/scala/lc/server/Server.scala b/src/main/scala/lc/server/Server.scala
index 73dff4b..cd33cf9 100644
--- a/src/main/scala/lc/server/Server.scala
+++ b/src/main/scala/lc/server/Server.scala
@@ -14,20 +14,21 @@ class Server(port: Int) {
 
   implicit val formats: DefaultFormats.type = DefaultFormats
   val server: HttpServer = HttpServer.create(new InetSocketAddress(port), 32)
+  server.setExecutor(java.util.concurrent.Executors.newCachedThreadPool())
 
   private def getRequestJson(ex: HttpExchange): JValue = {
     val requestBody = ex.getRequestBody
     val bytes = requestBody.readAllBytes
-    val string = bytes.map(_.toChar).mkString
+    val string = new String(bytes)
     parse(string)
   }
 
+  private val eqPattern = java.util.regex.Pattern.compile("=")
   private def getPathParameter(ex: HttpExchange): Either[String, Error] = {
     try {
-      val uri = ex.getRequestURI.toString
-      val pathParam = uri.split("\\?")(1)
-      val param = pathParam.split("=")
-      if (param(0) == "id") {
+      val query = ex.getRequestURI.getQuery
+      val param = eqPattern.split(query)
+      if(param(0) == "id"){
         Left(param(1))
       } else {
         Right(Error(ErrorMessageEnum.INVALID_PARAM.toString + "=> id"))
diff --git a/tests/locustfile.py b/tests/locustfile.py
index df55b4c..941c45e 100644
--- a/tests/locustfile.py
+++ b/tests/locustfile.py
@@ -19,7 +19,7 @@ def _(environment, **kw):
         environment.process_exit_code = 0
 
 class QuickStartUser(SequentialTaskSet):
-    wait_time = between(0.1,1)
+    wait_time = between(0.1,0.2)
 
     @task
     def captcha(self):
@@ -52,6 +52,6 @@ class QuickStartUser(SequentialTaskSet):
 
 
 class User(FastHttpUser):
-    wait_time = between(0.1,1)
+    wait_time = between(0.1,0.2)
     tasks = [QuickStartUser]
     host = "http://localhost:8888"
diff --git a/tests/run.sh b/tests/run.sh
index 34ed4fd..0d10e93 100755
--- a/tests/run.sh
+++ b/tests/run.sh
@@ -7,7 +7,7 @@ java -jar target/scala-2.13/LibreCaptcha.jar &
 JAVA_PID=$!
 sleep 4
 
-locust --headless -u 1000 -r 100 --run-time 4m --stop-timeout 30 -f tests/locustfile.py
+locust --headless -u 300 -r 100 --run-time 4m --stop-timeout 30 -f tests/locustfile.py
 status=$?
 
 kill $JAVA_PID