diff --git a/plugin/sql/jdbc/src/main/java/org/elasticsearch/xpack/sql/jdbc/net/client/JdbcHttpClient.java b/plugin/sql/jdbc/src/main/java/org/elasticsearch/xpack/sql/jdbc/net/client/JdbcHttpClient.java
index 30cccd96473..b376e39babd 100644
--- a/plugin/sql/jdbc/src/main/java/org/elasticsearch/xpack/sql/jdbc/net/client/JdbcHttpClient.java
+++ b/plugin/sql/jdbc/src/main/java/org/elasticsearch/xpack/sql/jdbc/net/client/JdbcHttpClient.java
@@ -23,6 +23,10 @@ import java.util.stream.Collectors;
 
 import static org.elasticsearch.xpack.sql.client.shared.StringUtils.EMPTY;
 
+/**
+ * JDBC specific HTTP client.
+ * Since JDBC is not thread-safe, neither is this class.
+ */
 public class JdbcHttpClient {
     private final HttpClient httpClient;
     private final JdbcConfiguration conCfg;
diff --git a/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/HttpClient.java b/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/HttpClient.java
index f72828f520c..1b885d5b1f9 100644
--- a/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/HttpClient.java
+++ b/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/HttpClient.java
@@ -38,7 +38,9 @@ import java.sql.SQLException;
 import java.util.function.Function;
 
 /**
- * A specialized high-level REST client with support for SQL-related functions
+ * A specialized high-level REST client with support for SQL-related functions.
+ * Similar to JDBC and the underlying HTTP connection, this class is not thread-safe
+ * and follows a request-response flow.
  */
 public class HttpClient {
 
@@ -85,7 +87,7 @@ public class HttpClient {
         return response.isSucceeded();
     }
     
-    private <Request extends AbstractSqlRequest, Response> Response post(String path, Request request, 
+    private <Request extends AbstractSqlRequest, Response> Response post(String path, Request request,
             CheckedFunction<XContentParser, Response, IOException> responseParser)
             throws SQLException {
         BytesReference requestBytes = toXContent(request);
diff --git a/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/shared/JreHttpUrlConnection.java b/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/shared/JreHttpUrlConnection.java
index ee4e758c08a..2f6289ee395 100644
--- a/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/shared/JreHttpUrlConnection.java
+++ b/plugin/sql/sql-shared-client/src/main/java/org/elasticsearch/xpack/sql/client/shared/JreHttpUrlConnection.java
@@ -5,9 +5,6 @@
  */
 package org.elasticsearch.xpack.sql.client.shared;
 
-import javax.net.ssl.HttpsURLConnection;
-import javax.net.ssl.SSLSocketFactory;
-import javax.sql.rowset.serial.SerialException;
 import java.io.BufferedInputStream;
 import java.io.Closeable;
 import java.io.IOException;
@@ -33,8 +30,17 @@ import java.util.Base64;
 import java.util.function.Function;
 import java.util.zip.GZIPInputStream;
 
+import javax.net.ssl.HttpsURLConnection;
+import javax.net.ssl.SSLSocketFactory;
+import javax.sql.rowset.serial.SerialException;
+
 import static java.util.Collections.emptyMap;
 
+/**
+ * Low-level http client using the built-in {@link HttpURLConnection}.
+ * As such, it has a stateless, on-demand, request-response flow without
+ * any connection pooling or sharing.
+ */
 public class JreHttpUrlConnection implements Closeable {
     /**
      * State added to {@link SQLException}s when the server encounters an
diff --git a/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/util/ReflectionUtils.java b/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/util/ReflectionUtils.java
index 60fb6ce61b5..0ddccccf7dd 100644
--- a/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/util/ReflectionUtils.java
+++ b/plugin/sql/src/main/java/org/elasticsearch/xpack/sql/util/ReflectionUtils.java
@@ -7,47 +7,12 @@ package org.elasticsearch.xpack.sql.util;
 
 import org.elasticsearch.xpack.sql.SqlIllegalArgumentException;
 
-import java.lang.reflect.GenericArrayType;
 import java.lang.reflect.ParameterizedType;
 import java.lang.reflect.Type;
-import java.lang.reflect.WildcardType;
 import java.util.Arrays;
 
 public class ReflectionUtils {
 
-    @SuppressWarnings("unchecked")
-    public static <E> Class<E> detectType(Type t) {
-        if (t instanceof Class<?>) {
-            return (Class<E>) t;
-        }
-        if (t instanceof ParameterizedType) {
-            Type[] typeArguments = ((ParameterizedType) t).getActualTypeArguments();
-            if (typeArguments.length != 1) {
-                throw new SqlIllegalArgumentException("Unexpected number of type arguments {} for {}", Arrays.toString(typeArguments), t);
-            }
-
-            return detectType(typeArguments[0]);
-        }
-        if (t instanceof WildcardType) {
-            WildcardType wt = (WildcardType) t;
-            if (wt.getLowerBounds().length == 1) {
-                return detectType(wt.getLowerBounds()[0]);
-            }
-            Type[] upperBounds = wt.getUpperBounds();
-
-            if (upperBounds.length != 1) {
-                throw new SqlIllegalArgumentException("Unexpected number of upper bounds {} for {}", Arrays.toString(upperBounds), t);
-            }
-
-            return detectType(upperBounds[0]);
-        }
-        if (t instanceof GenericArrayType) {
-            return detectType(((GenericArrayType) t).getGenericComponentType());
-        }
-
-        throw new SqlIllegalArgumentException("Unrecognized type {}", t);
-    }
-    
     @SuppressWarnings("unchecked")
     public static <E> Class<E> detectSuperTypeForRuleLike(Class<?> c) {
         Class<?> clazz = c;