diff --git a/core/src/main/java/org/elasticsearch/action/admin/cluster/node/info/NodeInfo.java b/core/src/main/java/org/elasticsearch/action/admin/cluster/node/info/NodeInfo.java
index 908a25a9abe..857f457ecae 100644
--- a/core/src/main/java/org/elasticsearch/action/admin/cluster/node/info/NodeInfo.java
+++ b/core/src/main/java/org/elasticsearch/action/admin/cluster/node/info/NodeInfo.java
@@ -20,6 +20,7 @@
 package org.elasticsearch.action.admin.cluster.node.info;
 
 import com.google.common.collect.ImmutableMap;
+
 import org.elasticsearch.Build;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.support.nodes.BaseNodeResponse;
@@ -75,7 +76,7 @@ public class NodeInfo extends BaseNodeResponse {
     NodeInfo() {
     }
 
-    public NodeInfo(Version version, Build build, DiscoveryNode node, @Nullable ImmutableMap<String, String> serviceAttributes, @Nullable Settings settings,
+    public NodeInfo(Version version, Build build, DiscoveryNode node, @Nullable Map<String, String> serviceAttributes, @Nullable Settings settings,
                     @Nullable OsInfo os, @Nullable ProcessInfo process, @Nullable JvmInfo jvm, @Nullable ThreadPoolInfo threadPool,
                     @Nullable TransportInfo transport, @Nullable HttpInfo http, @Nullable PluginsInfo plugins) {
         super(node);
diff --git a/core/src/main/java/org/elasticsearch/cluster/routing/IndexShardRoutingTable.java b/core/src/main/java/org/elasticsearch/cluster/routing/IndexShardRoutingTable.java
index e740a4fc67c..6512ee5cef7 100644
--- a/core/src/main/java/org/elasticsearch/cluster/routing/IndexShardRoutingTable.java
+++ b/core/src/main/java/org/elasticsearch/cluster/routing/IndexShardRoutingTable.java
@@ -19,7 +19,6 @@
 
 package org.elasticsearch.cluster.routing;
 
-import com.google.common.collect.ImmutableMap;
 import org.elasticsearch.cluster.node.DiscoveryNode;
 import org.elasticsearch.cluster.node.DiscoveryNodes;
 import org.elasticsearch.common.collect.MapBuilder;
@@ -39,6 +38,8 @@ import java.util.Map;
 import java.util.Set;
 import java.util.concurrent.ThreadLocalRandom;
 
+import static java.util.Collections.emptyMap;
+
 /**
  * {@link IndexShardRoutingTable} encapsulates all instances of a single shard.
  * Each Elasticsearch index consists of multiple shards, each shard encapsulates
@@ -60,6 +61,10 @@ public class IndexShardRoutingTable implements Iterable<ShardRouting> {
     final static List<ShardRouting> NO_SHARDS = Collections.emptyList();
     final boolean allShardsStarted;
 
+    private volatile Map<AttributesKey, AttributesRoutings> activeShardsByAttributes = emptyMap();
+    private volatile Map<AttributesKey, AttributesRoutings> initializingShardsByAttributes = emptyMap();
+    private final Object shardsByAttributeMutex = new Object();
+
     /**
      * The initializing list, including ones that are initializing on a target node because of relocation.
      * If we can come up with a better variable name, it would be nice...
@@ -476,10 +481,6 @@ public class IndexShardRoutingTable implements Iterable<ShardRouting> {
         }
     }
 
-    private volatile Map<AttributesKey, AttributesRoutings> activeShardsByAttributes = ImmutableMap.of();
-    private volatile Map<AttributesKey, AttributesRoutings> initializingShardsByAttributes = ImmutableMap.of();
-    private final Object shardsByAttributeMutex = new Object();
-
     private AttributesRoutings getActiveAttribute(AttributesKey key, DiscoveryNodes nodes) {
         AttributesRoutings shardRoutings = activeShardsByAttributes.get(key);
         if (shardRoutings == null) {
diff --git a/core/src/main/java/org/elasticsearch/common/inject/assistedinject/FactoryProvider.java b/core/src/main/java/org/elasticsearch/common/inject/assistedinject/FactoryProvider.java
index ea5a664ceb1..3837de81b60 100644
--- a/core/src/main/java/org/elasticsearch/common/inject/assistedinject/FactoryProvider.java
+++ b/core/src/main/java/org/elasticsearch/common/inject/assistedinject/FactoryProvider.java
@@ -16,8 +16,6 @@
 
 package org.elasticsearch.common.inject.assistedinject;
 
-import com.google.common.collect.ImmutableMap;
-
 import org.elasticsearch.common.inject.ConfigurationException;
 import org.elasticsearch.common.inject.Inject;
 import org.elasticsearch.common.inject.Injector;
@@ -42,6 +40,7 @@ import java.util.List;
 import java.util.Map;
 import java.util.Set;
 
+import static java.util.Collections.emptyMap;
 import static java.util.Collections.singleton;
 import static java.util.Collections.unmodifiableSet;
 
@@ -223,7 +222,7 @@ public class FactoryProvider<F> implements Provider<F>, HasDependencies {
         }
 
         if (constructors.isEmpty()) {
-            return ImmutableMap.of();
+            return emptyMap();
         }
 
         Method[] factoryMethods = factoryType.getRawType().getMethods();
diff --git a/core/src/main/java/org/elasticsearch/common/settings/Settings.java b/core/src/main/java/org/elasticsearch/common/settings/Settings.java
index e36843038da..663abd746f0 100644
--- a/core/src/main/java/org/elasticsearch/common/settings/Settings.java
+++ b/core/src/main/java/org/elasticsearch/common/settings/Settings.java
@@ -19,8 +19,6 @@
 
 package org.elasticsearch.common.settings;
 
-import java.nio.charset.StandardCharsets;
-import com.google.common.collect.ImmutableMap;
 import org.elasticsearch.Version;
 import org.elasticsearch.common.Booleans;
 import org.elasticsearch.common.Strings;
@@ -30,20 +28,40 @@ import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.common.property.PropertyPlaceholder;
 import org.elasticsearch.common.settings.loader.SettingsLoader;
 import org.elasticsearch.common.settings.loader.SettingsLoaderFactory;
-import org.elasticsearch.common.unit.*;
+import org.elasticsearch.common.unit.ByteSizeUnit;
+import org.elasticsearch.common.unit.ByteSizeValue;
+import org.elasticsearch.common.unit.MemorySizeValue;
+import org.elasticsearch.common.unit.RatioValue;
+import org.elasticsearch.common.unit.SizeValue;
+import org.elasticsearch.common.unit.TimeValue;
 import org.elasticsearch.common.xcontent.ToXContent;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Iterator;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Properties;
+import java.util.Set;
+import java.util.SortedMap;
+import java.util.TreeMap;
 import java.util.concurrent.TimeUnit;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
+import static java.util.Collections.emptyMap;
+import static java.util.Collections.unmodifiableMap;
 import static org.elasticsearch.common.Strings.toCamelCase;
 import static org.elasticsearch.common.unit.ByteSizeValue.parseBytesSizeValue;
 import static org.elasticsearch.common.unit.SizeValue.parseSizeValue;
@@ -70,8 +88,8 @@ public final class Settings implements ToXContent {
         return settingsRequireUnits;
     }
 
+    private final Map<String, String> forcedUnderscoreSettings;
     private SortedMap<String, String> settings;
-    private final ImmutableMap<String, String> forcedUnderscoreSettings;
 
     Settings(Map<String, String> settings) {
         // we use a sorted map for consistent serialization when using getAsMap()
@@ -86,7 +104,7 @@ public final class Settings implements ToXContent {
                 forcedUnderscoreSettings.put(toUnderscoreCase, entry.getValue());
             }
         }
-        this.forcedUnderscoreSettings = forcedUnderscoreSettings == null ? ImmutableMap.<String, String>of() : ImmutableMap.copyOf(forcedUnderscoreSettings);
+        this.forcedUnderscoreSettings = forcedUnderscoreSettings == null ? emptyMap() : unmodifiableMap(forcedUnderscoreSettings);
     }
 
     /**
diff --git a/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapper.java b/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapper.java
index 54b2c98b71d..0314f8f6aae 100644
--- a/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapper.java
+++ b/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapper.java
@@ -19,7 +19,6 @@
 
 package org.elasticsearch.index.mapper;
 
-import com.google.common.collect.ImmutableMap;
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.search.DocIdSet;
 import org.apache.lucene.search.DocIdSetIterator;
@@ -70,6 +69,8 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.locks.ReentrantReadWriteLock;
 
+import static java.util.Collections.emptyMap;
+
 /**
  *
  */
@@ -85,7 +86,7 @@ public class DocumentMapper implements ToXContent {
 
         private final RootObjectMapper rootObjectMapper;
 
-        private ImmutableMap<String, Object> meta = ImmutableMap.of();
+        private Map<String, Object> meta = emptyMap();
 
         private final Mapper.BuilderContext builderContext;
 
@@ -115,7 +116,7 @@ public class DocumentMapper implements ToXContent {
             this.rootMappers.put(FieldNamesFieldMapper.class, new FieldNamesFieldMapper(indexSettings, mapperService.fullName(FieldNamesFieldMapper.NAME)));
         }
 
-        public Builder meta(ImmutableMap<String, Object> meta) {
+        public Builder meta(Map<String, Object> meta) {
             this.meta = meta;
             return this;
         }
@@ -169,7 +170,7 @@ public class DocumentMapper implements ToXContent {
 
     public DocumentMapper(MapperService mapperService, @Nullable Settings indexSettings, DocumentMapperParser docMapperParser,
                           RootObjectMapper rootObjectMapper,
-                          ImmutableMap<String, Object> meta,
+                          Map<String, Object> meta,
                           Map<Class<? extends MetadataFieldMapper>, MetadataFieldMapper> rootMappers,
                           List<SourceTransform> sourceTransforms,
                           ReentrantReadWriteLock mappingLock) {
@@ -234,7 +235,7 @@ public class DocumentMapper implements ToXContent {
         return this.typeText;
     }
 
-    public ImmutableMap<String, Object> meta() {
+    public Map<String, Object> meta() {
         return mapping.meta;
     }
 
diff --git a/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapperParser.java b/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapperParser.java
index bb991ef2603..ed5c3b3de8f 100644
--- a/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapperParser.java
+++ b/core/src/main/java/org/elasticsearch/index/mapper/DocumentMapperParser.java
@@ -20,6 +20,7 @@
 package org.elasticsearch.index.mapper;
 
 import com.google.common.collect.ImmutableMap;
+
 import org.elasticsearch.Version;
 import org.elasticsearch.common.Nullable;
 import org.elasticsearch.common.ParseFieldMatcher;
@@ -35,10 +36,33 @@ import org.elasticsearch.common.xcontent.XContentFactory;
 import org.elasticsearch.common.xcontent.XContentHelper;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.index.analysis.AnalysisService;
-import org.elasticsearch.index.mapper.core.*;
+import org.elasticsearch.index.mapper.core.BinaryFieldMapper;
+import org.elasticsearch.index.mapper.core.BooleanFieldMapper;
+import org.elasticsearch.index.mapper.core.ByteFieldMapper;
+import org.elasticsearch.index.mapper.core.CompletionFieldMapper;
+import org.elasticsearch.index.mapper.core.DateFieldMapper;
+import org.elasticsearch.index.mapper.core.DoubleFieldMapper;
+import org.elasticsearch.index.mapper.core.FloatFieldMapper;
+import org.elasticsearch.index.mapper.core.IntegerFieldMapper;
+import org.elasticsearch.index.mapper.core.LongFieldMapper;
+import org.elasticsearch.index.mapper.core.ShortFieldMapper;
+import org.elasticsearch.index.mapper.core.StringFieldMapper;
+import org.elasticsearch.index.mapper.core.TokenCountFieldMapper;
+import org.elasticsearch.index.mapper.core.TypeParsers;
 import org.elasticsearch.index.mapper.geo.GeoPointFieldMapper;
 import org.elasticsearch.index.mapper.geo.GeoShapeFieldMapper;
-import org.elasticsearch.index.mapper.internal.*;
+import org.elasticsearch.index.mapper.internal.AllFieldMapper;
+import org.elasticsearch.index.mapper.internal.FieldNamesFieldMapper;
+import org.elasticsearch.index.mapper.internal.IdFieldMapper;
+import org.elasticsearch.index.mapper.internal.IndexFieldMapper;
+import org.elasticsearch.index.mapper.internal.ParentFieldMapper;
+import org.elasticsearch.index.mapper.internal.RoutingFieldMapper;
+import org.elasticsearch.index.mapper.internal.SourceFieldMapper;
+import org.elasticsearch.index.mapper.internal.TTLFieldMapper;
+import org.elasticsearch.index.mapper.internal.TimestampFieldMapper;
+import org.elasticsearch.index.mapper.internal.TypeFieldMapper;
+import org.elasticsearch.index.mapper.internal.UidFieldMapper;
+import org.elasticsearch.index.mapper.internal.VersionFieldMapper;
 import org.elasticsearch.index.mapper.ip.IpFieldMapper;
 import org.elasticsearch.index.mapper.object.ObjectMapper;
 import org.elasticsearch.index.mapper.object.RootObjectMapper;
@@ -47,8 +71,15 @@ import org.elasticsearch.index.similarity.SimilarityLookupService;
 import org.elasticsearch.script.Script;
 import org.elasticsearch.script.ScriptService;
 
-import java.util.*;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+import java.util.SortedMap;
+import java.util.TreeMap;
 
+import static java.util.Collections.unmodifiableMap;
 import static org.elasticsearch.index.mapper.MapperBuilders.doc;
 
 public class DocumentMapperParser {
@@ -240,11 +271,12 @@ public class DocumentMapperParser {
             }
         }
 
-        ImmutableMap<String, Object> attributes = ImmutableMap.of();
-        if (mapping.containsKey("_meta")) {
-            attributes = ImmutableMap.copyOf((Map<String, Object>) mapping.remove("_meta"));
+        Map<String, Object> meta = (Map<String, Object>) mapping.remove("_meta");
+        if (meta != null) {
+            // It may not be required to copy meta here to maintain immutability
+            // but the cost is pretty low here.
+            docBuilder.meta(unmodifiableMap(new HashMap<>(meta)));
         }
-        docBuilder.meta(attributes);
 
         checkNoRemainingFields(mapping, parserContext.indexVersionCreated(), "Root mapping definition has unsupported parameters: ");
 
diff --git a/core/src/main/java/org/elasticsearch/index/mapper/Mapping.java b/core/src/main/java/org/elasticsearch/index/mapper/Mapping.java
index c3b22c6f512..412bb56a785 100644
--- a/core/src/main/java/org/elasticsearch/index/mapper/Mapping.java
+++ b/core/src/main/java/org/elasticsearch/index/mapper/Mapping.java
@@ -59,9 +59,9 @@ public final class Mapping implements ToXContent {
     final MetadataFieldMapper[] metadataMappers;
     final ImmutableMap<Class<? extends MetadataFieldMapper>, MetadataFieldMapper> rootMappersMap;
     final SourceTransform[] sourceTransforms;
-    volatile ImmutableMap<String, Object> meta;
+    volatile Map<String, Object> meta;
 
-    public Mapping(Version indexCreated, RootObjectMapper rootObjectMapper, MetadataFieldMapper[] metadataMappers, SourceTransform[] sourceTransforms, ImmutableMap<String, Object> meta) {
+    public Mapping(Version indexCreated, RootObjectMapper rootObjectMapper, MetadataFieldMapper[] metadataMappers, SourceTransform[] sourceTransforms, Map<String, Object> meta) {
         this.indexCreated = indexCreated;
         this.root = rootObjectMapper;
         this.metadataMappers = metadataMappers;
@@ -119,7 +119,7 @@ public final class Mapping implements ToXContent {
             meta = mergeWith.meta;
         }
     }
-    
+
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         root.toXContent(builder, params, new ToXContent() {
diff --git a/core/src/main/java/org/elasticsearch/index/query/ParsedQuery.java b/core/src/main/java/org/elasticsearch/index/query/ParsedQuery.java
index d1a4ca5ab1c..1c219268a93 100644
--- a/core/src/main/java/org/elasticsearch/index/query/ParsedQuery.java
+++ b/core/src/main/java/org/elasticsearch/index/query/ParsedQuery.java
@@ -19,22 +19,31 @@
 
 package org.elasticsearch.index.query;
 
-import com.google.common.collect.ImmutableMap;
-
 import org.apache.lucene.search.Query;
 import org.elasticsearch.common.lucene.search.Queries;
 
+import java.util.Map;
+
+import static java.util.Collections.emptyMap;
+
 /**
  * The result of parsing a query.
- *
- *
  */
 public class ParsedQuery {
-
     private final Query query;
-    private final ImmutableMap<String, Query> namedFilters;
+    private final Map<String, Query> namedFilters;
 
-    public ParsedQuery(Query query, ImmutableMap<String, Query> namedFilters) {
+    /**
+     * Store the query and filters.
+     *
+     * @param query
+     *            the query
+     * @param namedFilters
+     *            an immutable Map containing the named filters. Good callers
+     *            use emptyMap or unmodifiableMap and copy the source to make
+     *            sure this is immutable.
+     */
+    public ParsedQuery(Query query, Map<String, Query> namedFilters) {
         this.query = query;
         this.namedFilters = namedFilters;
     }
@@ -46,7 +55,7 @@ public class ParsedQuery {
 
     public ParsedQuery(Query query) {
         this.query = query;
-        this.namedFilters = ImmutableMap.of();
+        this.namedFilters = emptyMap();
     }
 
     /**
@@ -56,11 +65,11 @@ public class ParsedQuery {
         return this.query;
     }
 
-    public ImmutableMap<String, Query> namedFilters() {
-        return this.namedFilters;
+    public Map<String, Query> namedFilters() {
+        return namedFilters;
     }
 
     public static ParsedQuery parsedMatchAllQuery() {
-        return new ParsedQuery(Queries.newMatchAllQuery(), ImmutableMap.<String, Query>of());
+        return new ParsedQuery(Queries.newMatchAllQuery(), emptyMap());
     }
 }
diff --git a/core/src/main/java/org/elasticsearch/indices/IndicesService.java b/core/src/main/java/org/elasticsearch/indices/IndicesService.java
index 3b24544267d..37941530dd0 100644
--- a/core/src/main/java/org/elasticsearch/indices/IndicesService.java
+++ b/core/src/main/java/org/elasticsearch/indices/IndicesService.java
@@ -98,6 +98,7 @@ import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.stream.Stream;
 
+import static java.util.Collections.emptyMap;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_REPLICAS;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_NUMBER_OF_SHARDS;
 import static org.elasticsearch.common.collect.MapBuilder.newMapBuilder;
@@ -121,8 +122,8 @@ public class IndicesService extends AbstractLifecycleComponent<IndicesService> i
     private final NodeEnvironment nodeEnv;
     private final TimeValue shardsClosedTimeout;
 
-    private volatile Map<String, IndexServiceInjectorPair> indices = ImmutableMap.of();
-    
+    private volatile Map<String, IndexServiceInjectorPair> indices = emptyMap();
+
     static class IndexServiceInjectorPair {
         private final IndexService indexService;
         private final Injector injector;
@@ -140,7 +141,7 @@ public class IndicesService extends AbstractLifecycleComponent<IndicesService> i
             return injector;
         }
     }
-    
+
     private final Map<Index, List<PendingDelete>> pendingDeletes = new HashMap<>();
 
     private final OldShardsStats oldShardsStats = new OldShardsStats();
@@ -347,7 +348,7 @@ public class IndicesService extends AbstractLifecycleComponent<IndicesService> i
         modules.add(new MapperServiceModule());
         modules.add(new IndexAliasesServiceModule());
         modules.add(new IndexModule(indexSettings));
-        
+
         pluginsService.processModules(modules);
 
         Injector indexInjector;
diff --git a/core/src/main/java/org/elasticsearch/node/service/NodeService.java b/core/src/main/java/org/elasticsearch/node/service/NodeService.java
index 369f7e084bf..d394765bcfc 100644
--- a/core/src/main/java/org/elasticsearch/node/service/NodeService.java
+++ b/core/src/main/java/org/elasticsearch/node/service/NodeService.java
@@ -19,8 +19,6 @@
 
 package org.elasticsearch.node.service;
 
-import com.google.common.collect.ImmutableMap;
-
 import org.elasticsearch.Build;
 import org.elasticsearch.Version;
 import org.elasticsearch.action.admin.cluster.node.info.NodeInfo;
@@ -44,6 +42,8 @@ import org.elasticsearch.transport.TransportService;
 import java.io.IOException;
 import java.util.Map;
 
+import static java.util.Collections.emptyMap;
+
 /**
  */
 public class NodeService extends AbstractComponent {
@@ -59,7 +59,7 @@ public class NodeService extends AbstractComponent {
     @Nullable
     private HttpServer httpServer;
 
-    private volatile ImmutableMap<String, String> serviceAttributes = ImmutableMap.of();
+    private volatile Map<String, String> serviceAttributes = emptyMap();
 
     private final Version version;
 
diff --git a/core/src/main/java/org/elasticsearch/search/internal/InternalSearchHit.java b/core/src/main/java/org/elasticsearch/search/internal/InternalSearchHit.java
index b421e4ac7a6..c1194f1f401 100644
--- a/core/src/main/java/org/elasticsearch/search/internal/InternalSearchHit.java
+++ b/core/src/main/java/org/elasticsearch/search/internal/InternalSearchHit.java
@@ -19,8 +19,6 @@
 
 package org.elasticsearch.search.internal;
 
-import com.google.common.collect.ImmutableMap;
-
 import org.apache.lucene.search.Explanation;
 import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.ElasticsearchParseException;
@@ -54,6 +52,8 @@ import java.util.List;
 import java.util.Map;
 
 import static java.util.Collections.emptyMap;
+import static java.util.Collections.singletonMap;
+import static java.util.Collections.unmodifiableMap;
 import static org.elasticsearch.common.lucene.Lucene.readExplanation;
 import static org.elasticsearch.common.lucene.Lucene.writeExplanation;
 import static org.elasticsearch.search.SearchShardTarget.readSearchShardTarget;
@@ -317,10 +317,7 @@ public class InternalSearchHit implements SearchHit {
 
     @Override
     public Map<String, HighlightField> highlightFields() {
-        if (highlightFields == null) {
-            return ImmutableMap.of();
-        }
-        return this.highlightFields;
+        return highlightFields == null ? emptyMap() : highlightFields;
     }
 
     @Override
@@ -573,69 +570,32 @@ public class InternalSearchHit implements SearchHit {
         }
         int size = in.readVInt();
         if (size == 0) {
-            fields = ImmutableMap.of();
+            fields = emptyMap();
         } else if (size == 1) {
             SearchHitField hitField = readSearchHitField(in);
-            fields = ImmutableMap.of(hitField.name(), hitField);
-        } else if (size == 2) {
-            SearchHitField hitField1 = readSearchHitField(in);
-            SearchHitField hitField2 = readSearchHitField(in);
-            fields = ImmutableMap.of(hitField1.name(), hitField1, hitField2.name(), hitField2);
-        } else if (size == 3) {
-            SearchHitField hitField1 = readSearchHitField(in);
-            SearchHitField hitField2 = readSearchHitField(in);
-            SearchHitField hitField3 = readSearchHitField(in);
-            fields = ImmutableMap.of(hitField1.name(), hitField1, hitField2.name(), hitField2, hitField3.name(), hitField3);
-        } else if (size == 4) {
-            SearchHitField hitField1 = readSearchHitField(in);
-            SearchHitField hitField2 = readSearchHitField(in);
-            SearchHitField hitField3 = readSearchHitField(in);
-            SearchHitField hitField4 = readSearchHitField(in);
-            fields = ImmutableMap.of(hitField1.name(), hitField1, hitField2.name(), hitField2, hitField3.name(), hitField3, hitField4.name(), hitField4);
-        } else if (size == 5) {
-            SearchHitField hitField1 = readSearchHitField(in);
-            SearchHitField hitField2 = readSearchHitField(in);
-            SearchHitField hitField3 = readSearchHitField(in);
-            SearchHitField hitField4 = readSearchHitField(in);
-            SearchHitField hitField5 = readSearchHitField(in);
-            fields = ImmutableMap.of(hitField1.name(), hitField1, hitField2.name(), hitField2, hitField3.name(), hitField3, hitField4.name(), hitField4, hitField5.name(), hitField5);
+            fields = singletonMap(hitField.name(), hitField);
         } else {
-            ImmutableMap.Builder<String, SearchHitField> builder = ImmutableMap.builder();
+            Map<String, SearchHitField> fields = new HashMap<>();
             for (int i = 0; i < size; i++) {
                 SearchHitField hitField = readSearchHitField(in);
-                builder.put(hitField.name(), hitField);
+                fields.put(hitField.name(), hitField);
             }
-            fields = builder.build();
+            this.fields = unmodifiableMap(fields);
         }
 
         size = in.readVInt();
         if (size == 0) {
-            highlightFields = ImmutableMap.of();
+            highlightFields = emptyMap();
         } else if (size == 1) {
             HighlightField field = readHighlightField(in);
-            highlightFields = ImmutableMap.of(field.name(), field);
-        } else if (size == 2) {
-            HighlightField field1 = readHighlightField(in);
-            HighlightField field2 = readHighlightField(in);
-            highlightFields = ImmutableMap.of(field1.name(), field1, field2.name(), field2);
-        } else if (size == 3) {
-            HighlightField field1 = readHighlightField(in);
-            HighlightField field2 = readHighlightField(in);
-            HighlightField field3 = readHighlightField(in);
-            highlightFields = ImmutableMap.of(field1.name(), field1, field2.name(), field2, field3.name(), field3);
-        } else if (size == 4) {
-            HighlightField field1 = readHighlightField(in);
-            HighlightField field2 = readHighlightField(in);
-            HighlightField field3 = readHighlightField(in);
-            HighlightField field4 = readHighlightField(in);
-            highlightFields = ImmutableMap.of(field1.name(), field1, field2.name(), field2, field3.name(), field3, field4.name(), field4);
+            highlightFields = singletonMap(field.name(), field);
         } else {
-            ImmutableMap.Builder<String, HighlightField> builder = ImmutableMap.builder();
+            Map<String, HighlightField> highlightFields = new HashMap<>();
             for (int i = 0; i < size; i++) {
                 HighlightField field = readHighlightField(in);
-                builder.put(field.name(), field);
+                highlightFields.put(field.name(), field);
             }
-            highlightFields = builder.build();
+            this.highlightFields = unmodifiableMap(highlightFields);
         }
 
         size = in.readVInt();
diff --git a/core/src/main/java/org/elasticsearch/snapshots/RestoreService.java b/core/src/main/java/org/elasticsearch/snapshots/RestoreService.java
index 3b8b2e1b1fa..1c7773e34b8 100644
--- a/core/src/main/java/org/elasticsearch/snapshots/RestoreService.java
+++ b/core/src/main/java/org/elasticsearch/snapshots/RestoreService.java
@@ -90,6 +90,7 @@ import java.util.Set;
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.CopyOnWriteArrayList;
 
+import static java.util.Collections.emptyMap;
 import static java.util.Collections.unmodifiableSet;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_AUTO_EXPAND_REPLICAS;
 import static org.elasticsearch.cluster.metadata.IndexMetaData.SETTING_CREATION_DATE;
@@ -232,7 +233,7 @@ public class RestoreService extends AbstractComponent implements ClusterStateLis
                     MetaData.Builder mdBuilder = MetaData.builder(currentState.metaData());
                     ClusterBlocks.Builder blocks = ClusterBlocks.builder().blocks(currentState.blocks());
                     RoutingTable.Builder rtBuilder = RoutingTable.builder(currentState.routingTable());
-                    final ImmutableMap<ShardId, RestoreInProgress.ShardRestoreStatus> shards;
+                    Map<ShardId, RestoreInProgress.ShardRestoreStatus> shards;
                     Set<String> aliases = new HashSet<>();
                     if (!renamedIndices.isEmpty()) {
                         // We have some indices to restore
@@ -311,7 +312,7 @@ public class RestoreService extends AbstractComponent implements ClusterStateLis
                         RestoreInProgress.Entry restoreEntry = new RestoreInProgress.Entry(snapshotId, RestoreInProgress.State.INIT, Collections.unmodifiableList(new ArrayList<>(renamedIndices.keySet())), shards);
                         builder.putCustom(RestoreInProgress.TYPE, new RestoreInProgress(restoreEntry));
                     } else {
-                        shards = ImmutableMap.of();
+                        shards = emptyMap();
                     }
 
                     checkAliasNameConflicts(renamedIndices, aliases);