diff --git a/pom.xml b/pom.xml
index 2b52c84..232e3c3 100644
--- a/pom.xml
+++ b/pom.xml
@@ -28,10 +28,11 @@
   <url>http://maven.apache.org</url>
 
   <dependencies>
+    <!-- https://mvnrepository.com/artifact/org.foundationdb/fdb-java -->
     <dependency>
-      <groupId>com.apple.cie.foundationdb</groupId>
+      <groupId>org.foundationdb</groupId>
       <artifactId>fdb-java</artifactId>
-      <version>5.1.5</version>
+      <version>7.3.43</version>
     </dependency>
     <dependency>
       <groupId>org.hdrhistogram</groupId>
@@ -60,6 +61,11 @@
       <version>4.11</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>org.roaringbitmap</groupId>
+      <artifactId>RoaringBitmap</artifactId>
+      <version>0.9.0</version>
+    </dependency>
   </dependencies>
 
   <properties>
diff --git a/src/main/java/nbdfdb/FDBBitSet.java b/src/main/java/nbdfdb/FDBBitSet.java
index 8bf5cd2..e667f00 100644
--- a/src/main/java/nbdfdb/FDBBitSet.java
+++ b/src/main/java/nbdfdb/FDBBitSet.java
@@ -19,15 +19,17 @@
 
 import com.apple.foundationdb.*;
 import com.apple.foundationdb.subspace.Subspace;
+import org.roaringbitmap.RoaringBitmap;
+import org.roaringbitmap.buffer.ImmutableRoaringBitmap;
+import org.roaringbitmap.buffer.MutableRoaringBitmap;
 
-import java.util.BitSet;
+import java.nio.ByteBuffer;
 import java.util.concurrent.CompletableFuture;
 
 public class FDBBitSet {
   private final Database database;
   private final Subspace subspace;
   private final int blockSize;
-  private final int bitsPerBlock;
   private final byte[] allSetBytes;
   private final Range subspaceRange;
 
@@ -35,10 +37,11 @@ protected FDBBitSet(Database database, Subspace subspace, int blockSize) {
     this.database = database;
     this.subspace = subspace;
     this.blockSize = blockSize;
-    bitsPerBlock = blockSize * 8;
-    BitSet allSet = new BitSet(bitsPerBlock);
-    allSet.set(0, bitsPerBlock);
-    allSetBytes = allSet.toByteArray();
+    RoaringBitmap allSet = new RoaringBitmap();
+    allSet.add(0L, blockSize * 8L);
+    ByteBuffer byteBuffer = ByteBuffer.allocate(allSet.serializedSizeInBytes());
+    allSet.serialize(byteBuffer);
+    allSetBytes = byteBuffer.array();
     subspaceRange = Range.startsWith(subspace.pack());
   }
 
@@ -50,37 +53,24 @@ public CompletableFuture<Void> set(long startBit, long endBit) {
   }
 
   protected void set(Transaction tx, long startBit, long endBit) {
-    long startBlock = startBit / bitsPerBlock;
-    long endBlock = endBit / bitsPerBlock;
-    BitSet bitSet = new BitSet(bitsPerBlock);
-    for (long block = startBlock; block <= endBlock; block++) {
-      bitSet.clear();
-      if (block == startBlock) {
-        int startBitOffset = (int) (startBit % bitsPerBlock);
-        int endBitOffset = startBlock == endBlock ? (int) (endBit % bitsPerBlock) : bitsPerBlock - 1;
-        bitSet.set(startBitOffset, endBitOffset + 1);
-        byte[] bitBytes = bitSet.toByteArray();
-        byte[] bytes = new byte[blockSize];
-        System.arraycopy(bitBytes, 0, bytes, 0, bitBytes.length);
-        tx.mutate(MutationType.BIT_OR, subspace.get(block).pack(), bytes);
-      } else if (block == endBlock) {
-        int endBitOffset = (int) (endBit % bitsPerBlock);
-        bitSet.set(0, endBitOffset);
-        byte[] bitBytes = bitSet.toByteArray();
-        byte[] bytes = new byte[blockSize];
-        System.arraycopy(bitBytes, 0, bytes, 0, bitBytes.length);
-        tx.mutate(MutationType.BIT_OR, subspace.get(block).pack(), bytes);
-      } else {
-        tx.set(subspace.get(block).pack(), allSetBytes);
-      }
-    }
+    // TODO: need to do something if the bitset is too big for an FDB value
+    MutableRoaringBitmap bitSet = new MutableRoaringBitmap();
+    bitSet.add(startBit, endBit + 1);
+    int capacity = bitSet.serializedSizeInBytes();
+    assert capacity <= 100_000;
+    ByteBuffer byteBuffer = ByteBuffer.allocate(capacity);
+    bitSet.serialize(byteBuffer);
+    byte[] bytes = byteBuffer.array();
+    tx.set(subspace.pack(), bytes);
   }
 
   public CompletableFuture<Long> count() {
     return database.runAsync(tx -> {
       long count = 0;
       for (KeyValue keyValue : tx.getRange(subspaceRange)) {
-        count += BitSet.valueOf(keyValue.getValue()).cardinality();
+        ByteBuffer byteBuffer = ByteBuffer.wrap(keyValue.getValue());
+        ImmutableRoaringBitmap bitSet = new ImmutableRoaringBitmap(byteBuffer);
+        count += bitSet.getLongCardinality();
       }
       return CompletableFuture.completedFuture(count);
     });