diff --git a/bench/index.js b/bench/index.js
index 7a8a55fbe..dfe260b65 100644
--- a/bench/index.js
+++ b/bench/index.js
@@ -10,7 +10,8 @@
 // in between.
 
 var newSuite  = require("./suite"),
-    payload   = require("./data/bench.json");
+    payload   = require("./data/bench.json"),
+    protobuf = require("..");
 
 var Buffer_from = Buffer.from !== Uint8Array.from && Buffer.from || function(value, encoding) { return new Buffer(value, encoding); };
 
@@ -88,3 +89,40 @@ newSuite("combined")
     jspbCls.deserializeBinary(jspbMsg.serializeBinary());
 })
 .run();
+
+var json = require("../tests/data/test.json");
+newSuite("fromJSON")
+.add("isolated", function() {
+    protobuf.Root.fromJSON(json);
+})
+.add("isolated (resolveAll)", function() {
+    protobuf.Root.fromJSON(json).resolveAll();
+})
+.add("shared (unique)", function() {
+    var root = protobuf.Root.fromJSON(json);
+    for (var i = 0; i < 1000; ++i) {
+        var jsonCopy = {
+            options: json.options,
+            nested: {}
+        };
+        // eslint-disable-next-line no-loop-func
+        Object.keys(json).forEach(key => {
+            jsonCopy.nested[key + i] = json[key];
+        });
+
+        protobuf.Root.fromJSON(jsonCopy, root);
+    }
+}).run();
+
+var resolveAllRoot = protobuf.Root.fromJSON(json);
+newSuite("resolveAll")
+.add("isolated", function() {
+    resolveAllRoot.resolveAll();
+}).run();
+
+newSuite("load")
+.add("sync", function() {
+    protobuf.loadSync("bench/data/bench.proto");
+})
+.run();
+
diff --git a/index.d.ts b/index.d.ts
index 6e211631d..fb96caec1 100644
--- a/index.d.ts
+++ b/index.d.ts
@@ -750,6 +750,9 @@ export abstract class NamespaceBase extends ReflectionObject {
     /** Nested objects by name. */
     public nested?: { [k: string]: ReflectionObject };
 
+    /** Whether or not objects contained in this namespace need feature resolution. */
+    protected _needsRecursiveFeatureResolution: boolean;
+
     /** Nested objects of this namespace as an array for iteration. */
     public readonly nestedArray: ReflectionObject[];
 
@@ -909,6 +912,9 @@ export abstract class ReflectionObject {
     /** Resolved Features. */
     public _features: object;
 
+    /** Whether or not features have been resolved. */
+    public _featuresResolved: boolean;
+
     /** Parent namespace. */
     public parent: (Namespace|null);
 
diff --git a/package.json b/package.json
index 717b5f105..df40083fe 100644
--- a/package.json
+++ b/package.json
@@ -33,7 +33,9 @@
     "build:bundle": "gulp --gulpfile scripts/gulpfile.js",
     "build:types": "node cli/bin/pbts --main --global protobuf --out index.d.ts src/ lib/aspromise/index.js lib/base64/index.js lib/codegen/index.js lib/eventemitter/index.js lib/float/index.js lib/fetch/index.js lib/inquire/index.js lib/path/index.js lib/pool/index.js lib/utf8/index.js",
     "changelog": "node scripts/changelog -w",
-    "coverage": "nyc tape -r ./lib/tape-adapter tests/*.js tests/node/*.js",
+    "coverage": "npm run coverage:test && npm run coverage:report",
+    "coverage:test": "nyc --silent tape -r ./lib/tape-adapter tests/*.js tests/node/*.js",
+    "coverage:report": "nyc report --reporter=lcov --reporter=text",
     "docs": "jsdoc -c config/jsdoc.json -R README.md --verbose --pedantic",
     "lint": "npm run lint:sources && npm run lint:types",
     "lint:sources": "eslint \"**/*.js\" -c config/eslint.json",
diff --git a/src/field.js b/src/field.js
index b71969e2e..72d8f63e0 100644
--- a/src/field.js
+++ b/src/field.js
@@ -370,12 +370,18 @@ Field.prototype._inferLegacyProtoFeatures = function _inferLegacyProtoFeatures(e
     }
 
     var features = {};
-    this.resolve();
+
     if (this.rule === "required") {
         features.field_presence = "LEGACY_REQUIRED";
     }
-    if (this.resolvedType instanceof Type && this.resolvedType.group) {
-        features.message_encoding = "DELIMITED";
+    if (this.parent && types.defaults[this.type] === undefined) {
+        // We can't use resolvedType because types may not have been resolved yet.  However,
+        // legacy groups are always in the same scope as the field so we don't have to do a
+        // full scan of the tree.
+        var type = this.parent.get(this.type.split(".").pop());
+        if (type && type instanceof Type && type.group) {
+            features.message_encoding = "DELIMITED";
+        }
     }
     if (this.getOption("packed") === true) {
         features.repeated_field_encoding = "PACKED";
diff --git a/src/namespace.js b/src/namespace.js
index 51ba2bd24..2a79f296a 100644
--- a/src/namespace.js
+++ b/src/namespace.js
@@ -108,10 +108,33 @@ function Namespace(name, options) {
      * @private
      */
     this._nestedArray = null;
+
+    /**
+     * Cache lookup calls for any objects contains anywhere under this namespace.
+     * This drastically speeds up resolve for large cross-linked protos where the same
+     * types are looked up repeatedly.
+     * @type {Object.<string,ReflectionObject|null>}
+     * @private
+     */
+    this._lookupCache = {};
+
+    /**
+     * Whether or not objects contained in this namespace need feature resolution.
+     * @type {boolean}
+     * @protected
+     */
+    this._needsRecursiveFeatureResolution = true;
 }
 
 function clearCache(namespace) {
     namespace._nestedArray = null;
+    namespace._lookupCache = {};
+
+    // Also clear parent caches, since they include nested lookups.
+    var parent = namespace;
+    while(parent = parent.parent) {
+        parent._lookupCache = {};
+    }
     return namespace;
 }
 
@@ -249,6 +272,14 @@ Namespace.prototype.add = function add(object) {
         }
     }
 
+    this._needsRecursiveFeatureResolution = true;
+
+    // Also clear parent caches, since they need to recurse down.
+    var parent = this;
+    while(parent = parent.parent) {
+        parent._needsRecursiveFeatureResolution = true;
+    }
+
     object.onAdd(this);
     return clearCache(this);
 };
@@ -324,6 +355,9 @@ Namespace.prototype.resolveAll = function resolveAll() {
  * @override
  */
 Namespace.prototype._resolveFeaturesRecursive = function _resolveFeaturesRecursive(edition) {
+    if (!this._needsRecursiveFeatureResolution) return this;
+    this._needsRecursiveFeatureResolution = false;
+
     edition = this._edition || edition;
 
     ReflectionObject.prototype._resolveFeaturesRecursive.call(this, edition);
@@ -341,7 +375,6 @@ Namespace.prototype._resolveFeaturesRecursive = function _resolveFeaturesRecursi
  * @returns {ReflectionObject|null} Looked up object or `null` if none could be found
  */
 Namespace.prototype.lookup = function lookup(path, filterTypes, parentAlreadyChecked) {
-
     /* istanbul ignore next */
     if (typeof filterTypes === "boolean") {
         parentAlreadyChecked = filterTypes;
@@ -360,25 +393,48 @@ Namespace.prototype.lookup = function lookup(path, filterTypes, parentAlreadyChe
     if (path[0] === "")
         return this.root.lookup(path.slice(1), filterTypes);
 
+    var found = this._lookupImpl(path);
+    if (found && (!filterTypes || filterTypes.indexOf(found.constructor) > -1)) {
+        return found;
+    }
+
+    // If there hasn't been a match, try again at the parent
+    if (this.parent === null || parentAlreadyChecked)
+        return null;
+    return this.parent.lookup(path, filterTypes);
+};
+
+/**
+ * Internal helper for lookup that handles searching just at this namespace and below along with caching.
+ * @param {string[]} path Path to look up
+ * @returns {ReflectionObject|null} Looked up object or `null` if none could be found
+ * @private
+ */
+Namespace.prototype._lookupImpl = function lookup(path) {
+    var flatPath = path.join(".");
+    if(Object.prototype.hasOwnProperty.call(this._lookupCache, flatPath)) {
+        return this._lookupCache[flatPath];
+    }
+
     // Test if the first part matches any nested object, and if so, traverse if path contains more
     var found = this.get(path[0]);
+    var exact = null;
     if (found) {
         if (path.length === 1) {
-            if (!filterTypes || filterTypes.indexOf(found.constructor) > -1)
-                return found;
-        } else if (found instanceof Namespace && (found = found.lookup(path.slice(1), filterTypes, true)))
-            return found;
+            exact = found;
+        } else if (found instanceof Namespace && (found = found._lookupImpl(path.slice(1))))
+            exact = found;
 
     // Otherwise try each nested namespace
-    } else
+    } else {
         for (var i = 0; i < this.nestedArray.length; ++i)
-            if (this._nestedArray[i] instanceof Namespace && (found = this._nestedArray[i].lookup(path, filterTypes, true)))
-                return found;
+            if (this._nestedArray[i] instanceof Namespace && (found = this._nestedArray[i]._lookupImpl(path)))
+                exact = found;
+    }
 
-    // If there hasn't been a match, try again at the parent
-    if (this.parent === null || parentAlreadyChecked)
-        return null;
-    return this.parent.lookup(path, filterTypes);
+    // Set this even when null, so that when we walk up the tree we can quickly bail on repeated checks back down.
+    this._lookupCache[flatPath] = exact;
+    return exact;
 };
 
 /**
diff --git a/src/object.js b/src/object.js
index bf367e267..0ea6a2334 100644
--- a/src/object.js
+++ b/src/object.js
@@ -67,6 +67,12 @@ function ReflectionObject(name, options) {
      */
     this._features = {};
 
+    /**
+     * Whether or not features have been resolved.
+     * @type {boolean}
+     */
+    this._featuresResolved = false;
+
     /**
      * Parent namespace.
      * @type {Namespace|null}
@@ -172,10 +178,8 @@ ReflectionObject.prototype.onRemove = function onRemove(parent) {
 ReflectionObject.prototype.resolve = function resolve() {
     if (this.resolved)
         return this;
-    if (this instanceof Root) {
-        this._resolveFeaturesRecursive(this._edition);
-        this.resolved = true;
-    }
+    if (this.root instanceof Root)
+        this.resolved = true; // only if part of a root
     return this;
 };
 
@@ -194,6 +198,10 @@ ReflectionObject.prototype._resolveFeaturesRecursive = function _resolveFeatures
  * @returns {undefined}
  */
 ReflectionObject.prototype._resolveFeatures = function _resolveFeatures(edition) {
+    if (this._featuresResolved) {
+        return;
+    }
+
     var defaults = {};
 
     /* istanbul ignore if */
@@ -217,6 +225,7 @@ ReflectionObject.prototype._resolveFeatures = function _resolveFeatures(edition)
             throw new Error("Unknown edition: " + edition);
         }
         this._features = Object.assign(defaults, protoFeatures || {});
+        this._featuresResolved = true;
         return;
     }
 
@@ -238,6 +247,7 @@ ReflectionObject.prototype._resolveFeatures = function _resolveFeatures(edition)
         // Sister fields should have the same features as their extensions.
         this.extensionField._features = this._features;
     }
+    this._featuresResolved = true;
 };
 
 /**
diff --git a/src/root.js b/src/root.js
index 8e3c72c4a..fa6e10be0 100644
--- a/src/root.js
+++ b/src/root.js
@@ -51,7 +51,7 @@ Root.fromJSON = function fromJSON(json, root) {
         root = new Root();
     if (json.options)
         root.setOptions(json.options);
-    return root.addJSON(json.nested).resolveAll();
+    return root.addJSON(json.nested)._resolveFeaturesRecursive();
 };
 
 /**
@@ -99,6 +99,9 @@ Root.prototype.load = function load(filename, options, callback) {
 
     // Finishes loading by calling the callback (exactly once)
     function finish(err, root) {
+        if (root) {
+            root._resolveFeaturesRecursive();
+        }
         /* istanbul ignore if */
         if (!callback) {
             return;
@@ -108,9 +111,6 @@ Root.prototype.load = function load(filename, options, callback) {
         }
         var cb = callback;
         callback = null;
-        if (root) {
-            root.resolveAll();
-        }
         cb(err, root);
     }
 
@@ -218,8 +218,8 @@ Root.prototype.load = function load(filename, options, callback) {
     for (var i = 0, resolved; i < filename.length; ++i)
         if (resolved = self.resolvePath("", filename[i]))
             fetch(resolved);
-    self.resolveAll();
     if (sync) {
+        self._resolveFeaturesRecursive();
         return self;
     }
     if (!queued) {
@@ -272,6 +272,7 @@ Root.prototype.resolveAll = function resolveAll() {
         throw Error("unresolvable extensions: " + this.deferred.map(function(field) {
             return "'extend " + field.extend + "' in " + field.parent.fullName;
         }).join(", "));
+    this._resolveFeaturesRecursive(this._edition);
     return Namespace.prototype.resolveAll.call(this);
 };
 
diff --git a/src/service.js b/src/service.js
index 2c11ec9e3..a7be2f483 100644
--- a/src/service.js
+++ b/src/service.js
@@ -121,6 +121,8 @@ Service.prototype.resolveAll = function resolveAll() {
  * @override
  */
 Service.prototype._resolveFeaturesRecursive = function _resolveFeaturesRecursive(edition) {
+    if (!this._needsRecursiveFeatureResolution) return this;
+
     edition = this._edition || edition;
 
     Namespace.prototype._resolveFeaturesRecursive.call(this, edition);
diff --git a/src/type.js b/src/type.js
index 40c9f7868..c11fc6d65 100644
--- a/src/type.js
+++ b/src/type.js
@@ -317,6 +317,8 @@ Type.prototype.resolveAll = function resolveAll() {
  * @override
  */
 Type.prototype._resolveFeaturesRecursive = function _resolveFeaturesRecursive(edition) {
+    if (!this._needsRecursiveFeatureResolution) return this;
+
     edition = this._edition || edition;
 
     Namespace.prototype._resolveFeaturesRecursive.call(this, edition);