Squeezed the last bits I possibly can out of the Lua implementation.

Performance enhancements beyond what I've done are welcome.

src/main/java/com/imaginarycode/minecraft/redisbungee/RedisBungee.java

@@ -30,7 +30,6 @@ import com.google.common.base.Functions;
 import com.google.common.collect.*;
 import com.google.common.io.ByteStreams;
 import com.google.gson.Gson;
-import com.google.gson.reflect.TypeToken;
 import com.imaginarycode.minecraft.redisbungee.events.PubSubMessageEvent;
 import com.imaginarycode.minecraft.redisbungee.util.LuaManager;
 import com.imaginarycode.minecraft.redisbungee.util.NameFetcher;
@@ -55,7 +54,6 @@ import redis.clients.jedis.exceptions.JedisConnectionException;
 import redis.clients.jedis.exceptions.JedisException;
 
 import java.io.*;
-import java.nio.charset.StandardCharsets;
 import java.util.*;
 import java.util.concurrent.*;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -138,13 +136,22 @@ public final class RedisBungee extends Plugin {
 
     final Multimap<String, UUID> serversToPlayers() {
         if (usingLua) {
-            String string = (String) serverToPlayersScript.eval(ImmutableList.<String>of(), getServerIds());
-            Map<String, Set<UUID>> deserialized = gson.fromJson(string, new TypeToken<Map<String, Set<UUID>>>() {}.getType());
+            Collection<String> data = (Collection<String>) serverToPlayersScript.eval(ImmutableList.<String>of(), getServerIds());
 
             ImmutableMultimap.Builder<String, UUID> builder = ImmutableMultimap.builder();
 
-            for (Map.Entry<String, Set<UUID>> entry : deserialized.entrySet()) {
-                builder.putAll(entry.getKey(), entry.getValue());
+            // TODO: This seems pretty slow, but execution times over the long term seem to stay below that of the
+            // Java implementation, at least. If you have a better idea, I want to see it!
+            String key = null;
+
+            for (String s : data) {
+                if (key == null) {
+                    key = s;
+                    continue;
+                }
+
+                builder.put(key, UUID.fromString(s));
+                key = null;
             }
 
             return builder.build();

src/main/resources/lua/server_to_players.lua

@@ -1,5 +1,3 @@
--- This script needs all active proxies available specified as args.
-local insert = table.insert
 local call = redis.call
 
 local serverToData = {}
@@ -9,15 +7,11 @@ for _, proxy in ipairs(ARGV) do
     for _, player in ipairs(players) do
         local server = call("HGET", "player:" .. player, "server")
         if server then
-            local map = serverToData[server]
-            if not map then
-                map = {}
-                serverToData[server] = map
-            end
-            insert(map, player)
+            local sz = #serverToData
+            serverToData[sz + 1] = server
+            serverToData[sz + 2] = player
         end
     end
 end
 
--- Redis can't map Lua associative tables back, so we have to send it as JSON.
-return cjson.encode(serverToData)
+return serverToData