diff --git a/js/Gruntfile.js b/js/Gruntfile.js
index d1bd95a..17b311e 100644
--- a/js/Gruntfile.js
+++ b/js/Gruntfile.js
@@ -49,6 +49,7 @@ module.exports = grunt => {
       const server = new ContinuousServer( useRootDir );
       server.startServer( port );
       server.generateReportLoop();
+      server.computeWeightsLoop();
 
       if ( snapshot ) {
         server.createSnapshotLoop();
diff --git a/js/server/ContinuousServer.js b/js/server/ContinuousServer.js
index d6e90ad..8261ccb 100644
--- a/js/server/ContinuousServer.js
+++ b/js/server/ContinuousServer.js
@@ -334,14 +334,10 @@ class ContinuousServer {
    * @returns {number}
    */
   getTestWeight( test ) {
-    const lastTestedIndex = _.findIndex( this.snapshots, snapshot => {
-      const snapshotTest = snapshot.findTest( test.names );
-      return snapshotTest && snapshotTest.results.length > 0;
-    } );
-    const lastFailedIndex = _.findIndex( this.snapshots, snapshot => {
-      const snapshotTest = snapshot.findTest( test.names );
-      return snapshotTest && _.some( snapshotTest.results, testResult => !testResult.passed );
-    } );
+    const snapshotTests = this.snapshots.map( snapshot => snapshot.findTest( test.names ) ).filter( test => !!test );
+
+    const lastTestedIndex = _.findIndex( snapshotTests, snapshotTest => snapshotTest.results.length > 0 );
+    const lastFailedIndex = _.findIndex( snapshotTests, snapshotTest => _.some( snapshotTest.results, testResult => !testResult.passed ) );
 
     let weight = test.priority;
 
@@ -387,6 +383,16 @@ class ContinuousServer {
     return weight;
   }
 
+  /**
+   * Recomputes the desired weights for all recent tests.
+   * @private
+   */
+  computeRecentTestWeights() {
+    this.snapshots.slice( 0, 2 ).forEach( snapshot => snapshot.tests.forEach( test => {
+      test.weight = this.getTestWeight( test );
+    } ) );
+  }
+
   /**
    * Picks a test based on the tests' relative weights.
    * @public
@@ -397,7 +403,7 @@ class ContinuousServer {
   weightedSampleTest( tests ) {
     assert( tests.length );
 
-    const weights = tests.map( test => this.getTestWeight( test ) );
+    const weights = tests.map( test => test.weight );
     const totalWeight = _.sum( weights );
 
     const cutoffWeight = totalWeight * Math.random();
@@ -477,6 +483,8 @@ class ContinuousServer {
       await snapshot.create( true );
 
       this.snapshots.push( snapshot );
+
+      this.computeRecentTestWeights();
     }
 
     while ( !this.useRootDir ) {
@@ -528,6 +536,8 @@ class ContinuousServer {
               this.snapshots.pop();
             }
 
+            this.computeRecentTestWeights();
+
             this.saveToFile();
 
             this.setStatus( 'Removing old snapshot files' );
@@ -629,9 +639,25 @@ class ContinuousServer {
     }
   }
 
+  /**
+   * Starts computing weights for tests.
+   * @public
+   */
+  async computeWeightsLoop() {
+    while ( true ) { // eslint-disable-line
+      try {
+        this.computeRecentTestWeights();
+      }
+      catch ( e ) {
+        this.setError( `weights error: ${e}` );
+      }
+
+      await sleep( 30 * 1000 );
+    }
+  }
+
   /**
    * Starts generating reports from the available data.
-   *
    * @public
    */
   async generateReportLoop() {
@@ -688,7 +714,7 @@ class ContinuousServer {
         for ( const names of testNames ) {
           const test = this.snapshots[ 0 ] && this.snapshots[ 0 ].findTest( names );
           if ( test ) {
-            testWeights.push( Math.ceil( this.getTestWeight( test ) * 100 ) / 100 );
+            testWeights.push( Math.ceil( test.weight * 100 ) / 100 );
           }
           else {
             testWeights.push( 0 );
diff --git a/js/server/Snapshot.js b/js/server/Snapshot.js
index 3737d3c..86c87cd 100644
--- a/js/server/Snapshot.js
+++ b/js/server/Snapshot.js
@@ -125,6 +125,12 @@ class Snapshot {
       return new Test( this, description, lastRepoTimestamps[ potentialRepo ] || 0, lastRunnableTimestamps[ potentialRepo ] || 0 );
     } );
 
+    // @public {Object.<nameString:string,Test>} - ephemeral, we use this.tests for saving things
+    this.testMap = {};
+    this.tests.forEach( test => {
+      this.testMap[ test.nameString ] = test;
+    } );
+
     this.constructed = true;
   }
 
@@ -150,8 +156,7 @@ class Snapshot {
    * @returns {Test|null}
    */
   findTest( names ) {
-    // TODO: can increase performance with different lookups (e.g. binary?)
-    return _.find( this.tests, test => _.isEqual( test.names, names ) );
+    return this.testMap[ Test.namesToNameString( names ) ] || null;
   }
 
   /**
diff --git a/js/server/Test.js b/js/server/Test.js
index c521dd4..bcd6b9d 100644
--- a/js/server/Test.js
+++ b/js/server/Test.js
@@ -48,6 +48,9 @@ class Test {
     // @public {Array.<string>}
     this.names = description.test;
 
+    // @public {string} - Used for faster lookups, single tests, etc. - ephemeral
+    this.nameString = Test.namesToNameString( this.names );
+
     // @public {string}
     this.type = description.type;
 
@@ -57,6 +60,9 @@ class Test {
     // @public {number}
     this.priority = 1;
 
+    // @public {number} - ephemeral
+    this.weight = 1; // a default so things will work in case it isn't immediately set
+
     if ( description.priority ) {
       assert( typeof description.priority === 'number', 'priority should be a number' );
 
@@ -223,6 +229,17 @@ class Test {
     };
   }
 
+  /**
+   * Returns a single string from a list of names
+   * @public
+   *
+   * @param {Array.<string>} names
+   * @returns {string}
+   */
+  static namesToNameString( names ) {
+    return names.join( '.' );
+  }
+
   /**
    * Creates a pojo-style object for saving/restoring
    * @public