diff --git a/benchmarks/log-append.js b/benchmarks/log-append.js
index 894f1a4..48ab3b1 100644
--- a/benchmarks/log-append.js
+++ b/benchmarks/log-append.js
@@ -37,14 +37,17 @@ const queryLoop = async () => {
   // in case we want to benchmark different storage modules
   const entryStorage = await MemoryStorage()
   const headsStorage = await MemoryStorage()
+  const indexStorage = await MemoryStorage()
   // Test LRUStorage
   // const entryStorage = await LRUStorage()
   // const headsStorage = await LRUStorage()
+  // const indexStorage = await LRUStorage()
   // Test LevelStorage
   // const entryStorage = await LevelStorage({ path: './logA/entries' })
   // const headsStorage = await LevelStorage({ path: './logA/heads' })
+  // const indexStorage = await LevelStorage({ path: './logA/index' })
 
-  log = await Log(testIdentity, { logId: 'A', entryStorage, headsStorage })
+  log = await Log(testIdentity, { logId: 'A', entryStorage, headsStorage, indexStorage })
 
   // Output metrics at 1 second interval
   const interval = setInterval(async () => {
diff --git a/benchmarks/log-iterator.js b/benchmarks/log-iterator.js
index d904074..4da047b 100644
--- a/benchmarks/log-iterator.js
+++ b/benchmarks/log-iterator.js
@@ -15,14 +15,17 @@ import rmrf from 'rimraf'
   // in case we want to benchmark different storage modules
   const entryStorage = await MemoryStorage()
   const headsStorage = await MemoryStorage()
+  const indexStorage = await MemoryStorage()
   // Test LRUStorage
   // const entryStorage = await LRUStorage()
   // const headsStorage = await LRUStorage()
+  // const indexStorage = await LRUStorage()
   // Test LevelStorage
   // const entryStorage = await LevelStorage({ path: './logA/entries' })
   // const headsStorage = await LevelStorage({ path: './logA/heads' })
+  // const indexStorage = await LevelStorage({ path: './logA/index' })
 
-  const log = await Log(testIdentity, { logId: 'A', entryStorage, headsStorage })
+  const log = await Log(testIdentity, { logId: 'A', entryStorage, headsStorage, indexStorage })
 
   const entryCount = 10000
 
diff --git a/src/OrbitDB.js b/src/OrbitDB.js
index 1f5c2c3..a41e0e5 100644
--- a/src/OrbitDB.js
+++ b/src/OrbitDB.js
@@ -48,7 +48,7 @@ const OrbitDB = async ({ ipfs, id, identity, keystore, directory } = {}) => {
   directory = directory || './orbitdb'
   keystore = keystore || await KeyStore({ path: path.join(directory, './keystore') })
   const identities = await Identities({ ipfs, keystore })
-  identity = identity || await identities.createIdentity({ id, keystore })
+  identity = identity || await identities.createIdentity({ id })
 
   const manifestStorage = await ComposedStorage(
     await LRUStorage({ size: 1000 }),
diff --git a/src/database.js b/src/database.js
index 9e485ef..5b7af4b 100644
--- a/src/database.js
+++ b/src/database.js
@@ -7,7 +7,7 @@ import { ComposedStorage, LRUStorage, IPFSBlockStorage, LevelStorage } from './s
 const defaultPointerCount = 0
 const defaultCacheSize = 1000
 
-const Database = async ({ OpLog, ipfs, identity, address, name, accessController, directory, meta, headsStorage, entryStorage, pointerCount, syncAutomatically }) => {
+const Database = async ({ OpLog, ipfs, identity, address, name, accessController, directory, meta, headsStorage, entryStorage, indexStorage, pointerCount, syncAutomatically }) => {
   const { Log, Entry } = OpLog
 
   directory = Path.join(directory || './orbitdb', `./${address}/`)
@@ -24,10 +24,12 @@ const Database = async ({ OpLog, ipfs, identity, address, name, accessController
     await LevelStorage({ path: Path.join(directory, '/log/_heads/') })
   )
 
-  const log = await Log(identity, { logId: address, access: accessController, entryStorage, headsStorage })
+  indexStorage = indexStorage || await ComposedStorage(
+    await LRUStorage({ size: defaultCacheSize }),
+    await LevelStorage({ path: Path.join(directory, '/log/_index/') })
+  )
 
-  // const indexStorage = await LevelStorage({ path: Path.join(directory, '/log/_index/') })
-  // const log = await Log(identity, { logId: address.toString(), access: accessController, entryStorage, headsStorage, indexStorage })
+  const log = await Log(identity, { logId: address, access: accessController, entryStorage, headsStorage, indexStorage })
 
   const events = new EventEmitter()
   const queue = new PQueue({ concurrency: 1 })
diff --git a/src/key-store.js b/src/key-store.js
index c73e91b..144d9bc 100644
--- a/src/key-store.js
+++ b/src/key-store.js
@@ -21,7 +21,7 @@ const verifySignature = async (signature, publicKey, data) => {
   }
 
   if (!(data instanceof Uint8Array)) {
-    data = typeof data === "string" ? uint8ArrayFromString(data) : new Uint8Array(data)
+    data = typeof data === 'string' ? uint8ArrayFromString(data) : new Uint8Array(data)
   }
 
   const isValid = (key, msg, sig) => key.verify(msg, sig)
@@ -46,8 +46,8 @@ const signMessage = async (key, data) => {
     throw new Error('Given input data was undefined')
   }
 
-	if (!(data instanceof Uint8Array)) {
-    data = typeof data === "string" ? uint8ArrayFromString(data) : new Uint8Array(data)
+  if (!(data instanceof Uint8Array)) {
+    data = typeof data === 'string' ? uint8ArrayFromString(data) : new Uint8Array(data)
   }
 
   return uint8ArrayToString(await key.sign(data), 'base16')
diff --git a/src/oplog/log.js b/src/oplog/log.js
index a8351a2..11f057d 100644
--- a/src/oplog/log.js
+++ b/src/oplog/log.js
@@ -4,10 +4,6 @@ import Clock from './lamport-clock.js'
 import Heads from './heads.js'
 import Sorting from './sorting.js'
 import MemoryStorage from '../storage/memory.js'
-// import LRUStorage from './storage/lru.js'
-// import LevelStorage from './storage/level.js'
-// import IPFSBlockStorage from './storage/ipfs-block.js'
-// import ComposedStorage from './storage/composed.js'
 import { isDefined } from '../utils/index.js'
 
 const { LastWriteWins, NoZeroes } = Sorting
@@ -17,9 +13,6 @@ const maxClockTimeReducer = (res, acc) => Math.max(res, acc.clock.time)
 
 // Default storage for storing the Log and its entries. Default: Memory. Options: Memory, LRU, IPFS.
 const DefaultStorage = MemoryStorage
-// const DefaultStorage = LRUStorage
-// const DefaultStorage = LevelStorage
-// const DefaultStorage = IPFSBlockStorage
 
 // Default AccessController for the Log.
 // Default policy is that anyone can write to the Log.
@@ -69,7 +62,7 @@ const Log = async (identity, { logId, logHeads, access, entryStorage, headsStora
   // Oplog entry storage
   const _entries = entryStorage || await DefaultStorage()
   // Entry index for keeping track which entries are already in the log
-  // const _index = indexStorage || await DefaultStorage()
+  const _index = indexStorage || await DefaultStorage()
   // Heads storage
   headsStorage = headsStorage || await DefaultStorage()
   // Add heads to the state storage, ie. init the log state
@@ -117,15 +110,14 @@ const Log = async (identity, { logId, logHeads, access, entryStorage, headsStora
     const bytes = await _entries.get(hash)
     if (bytes) {
       const entry = await Entry.decode(bytes)
-      // await _index.put(hash, true)
+      await _index.put(hash, true)
       return entry
     }
   }
 
   const has = async (hash) => {
-    return false
-    // const entry = await _index.get(hash)
-    // return isDefined(entry)
+    const entry = await _index.get(hash)
+    return isDefined(entry)
   }
 
   /**
@@ -163,7 +155,7 @@ const Log = async (identity, { logId, logHeads, access, entryStorage, headsStora
     // Add entry to the entry storage
     await _entries.put(entry.hash, entry.bytes)
     // Add entry to the entry index
-    // await _index.put(entry.hash, true)
+    await _index.put(entry.hash, true)
     // Return the appended entry
     return entry
   }
@@ -207,6 +199,15 @@ const Log = async (identity, { logId, logHeads, access, entryStorage, headsStora
     const isAlreadyInTheLog = await has(entry.hash)
     if (isAlreadyInTheLog) {
       return false
+    } else {
+      // Check that the entry is not an entry that hasn't been indexed
+      const it = traverse(await heads(), (e) => e.next.includes(entry.hash))
+      for await (const e of it) {
+        if (e.next.includes(entry.hash)) {
+          await _index.put(entry.hash, true)
+          return false
+        }
+      }
     }
     // Check that the Entry belongs to this Log
     if (entry.id !== id) {
@@ -233,7 +234,7 @@ const Log = async (identity, { logId, logHeads, access, entryStorage, headsStora
     // Add the new entry to the entry storage
     await _entries.put(entry.hash, entry.bytes)
     // Add the new entry to the entry index
-    // await _index.put(entry.hash, true)
+    await _index.put(entry.hash, true)
     // We've added the entry to the log
     return true
   }
@@ -393,13 +394,13 @@ const Log = async (identity, { logId, logHeads, access, entryStorage, headsStora
   }
 
   const clear = async () => {
-    // await _index.clear()
+    await _index.clear()
     await _heads.clear()
     await _entries.clear()
   }
 
   const close = async () => {
-    // await _index.close()
+    await _index.close()
     await _heads.close()
     await _entries.close()
   }
@@ -451,6 +452,7 @@ const Log = async (identity, { logId, logHeads, access, entryStorage, headsStora
     values,
     all: values, // Alias for values()
     get,
+    has,
     append,
     join,
     joinEntry,
diff --git a/src/storage/ipfs-block.js b/src/storage/ipfs-block.js
index d181056..ade6d20 100644
--- a/src/storage/ipfs-block.js
+++ b/src/storage/ipfs-block.js
@@ -20,9 +20,7 @@ const IPFSBlockStorage = async ({ ipfs, timeout, pin } = {}) => {
     })
   }
 
-  const del = async (hash) => {
-    // TODO?
-  }
+  const del = async (hash) => {}
 
   const get = async (hash) => {
     const cid = CID.parse(hash, base58btc)
@@ -34,8 +32,6 @@ const IPFSBlockStorage = async ({ ipfs, timeout, pin } = {}) => {
 
   const iterator = async function * () {}
 
-  // TODO: all()
-
   const merge = async (other) => {}
 
   const clear = async () => {}
@@ -47,7 +43,6 @@ const IPFSBlockStorage = async ({ ipfs, timeout, pin } = {}) => {
     del,
     get,
     iterator,
-    // TODO: all,
     merge,
     clear,
     close
diff --git a/src/storage/level.js b/src/storage/level.js
index 28f0e32..663b29f 100644
--- a/src/storage/level.js
+++ b/src/storage/level.js
@@ -34,8 +34,6 @@ const LevelStorage = async ({ path, valueEncoding } = {}) => {
     }
   }
 
-  // TODO: all()
-
   const merge = async (other) => {}
 
   const clear = async () => {
@@ -51,7 +49,6 @@ const LevelStorage = async ({ path, valueEncoding } = {}) => {
     del,
     get,
     iterator,
-    // TODO: all,
     merge,
     clear,
     close
diff --git a/src/storage/lru.js b/src/storage/lru.js
index 62d09b2..e6f0ff3 100644
--- a/src/storage/lru.js
+++ b/src/storage/lru.js
@@ -24,8 +24,6 @@ const LRUStorage = async ({ size } = {}) => {
     }
   }
 
-  // TODO: all()
-
   const merge = async (other) => {
     if (other) {
       for await (const [key, value] of other.iterator()) {
@@ -45,7 +43,6 @@ const LRUStorage = async ({ size } = {}) => {
     del,
     get,
     iterator,
-    // TODO: all,
     merge,
     clear,
     close
diff --git a/src/storage/memory.js b/src/storage/memory.js
index ac15145..a1ddbf7 100644
--- a/src/storage/memory.js
+++ b/src/storage/memory.js
@@ -27,8 +27,6 @@ const MemoryStorage = async () => {
     }
   }
 
-  // TODO: all()
-
   const clear = async () => {
     memory = {}
   }
@@ -40,7 +38,6 @@ const MemoryStorage = async () => {
     del,
     get,
     iterator,
-    // TODO: all,
     merge,
     clear,
     close
diff --git a/test/access-controllers/ipfs-access-controller.test.js b/test/access-controllers/ipfs-access-controller.test.js
index bfe160a..3a7e38e 100644
--- a/test/access-controllers/ipfs-access-controller.test.js
+++ b/test/access-controllers/ipfs-access-controller.test.js
@@ -14,6 +14,7 @@ describe('IPFSAccessController', function () {
   this.timeout(config.timeout)
 
   let ipfs1, ipfs2
+  let keystore1, keystore2
   let identities1, identities2
   let testIdentity1, testIdentity2
 
@@ -22,8 +23,8 @@ describe('IPFSAccessController', function () {
     ipfs2 = await IPFS.create({ ...config.daemon2, repo: './ipfs2' })
     await connectPeers(ipfs1, ipfs2)
 
-    const keystore1 = await Keystore({ path: dbPath1 + '/keys' })
-    const keystore2 = await Keystore({ path: dbPath2 + '/keys' })
+    keystore1 = await Keystore({ path: dbPath1 + '/keys' })
+    keystore2 = await Keystore({ path: dbPath2 + '/keys' })
 
     identities1 = await Identities({ keystore: keystore1 })
     identities2 = await Identities({ keystore: keystore2 })
@@ -41,6 +42,14 @@ describe('IPFSAccessController', function () {
       await ipfs2.stop()
     }
 
+    if (keystore1) {
+      await keystore1.close()
+    }
+
+    if (keystore2) {
+      await keystore2.close()
+    }
+
     await rmrf('./orbitdb')
     await rmrf('./ipfs1')
     await rmrf('./ipfs2')
diff --git a/test/config.js b/test/config.js
index 258ac00..813e4f3 100644
--- a/test/config.js
+++ b/test/config.js
@@ -32,6 +32,7 @@ export default {
     }
   },
   daemon1: {
+    silent: true,
     EXPERIMENTAL: {
       pubsub: true
     },
@@ -54,6 +55,7 @@ export default {
     }
   },
   daemon2: {
+    silent: true,
     EXPERIMENTAL: {
       pubsub: true
     },
diff --git a/test/database-replication.test.js b/test/database-replication.test.js
index 1dcfa37..2d15664 100644
--- a/test/database-replication.test.js
+++ b/test/database-replication.test.js
@@ -83,27 +83,25 @@ describe('Database - Replication', function () {
     })
 
     it('replicates databases across two peers', async () => {
-      let connected1 = false
-      let connected2 = false
+      let replicated = false
+      let expectedEntryHash = null
 
-      const onConnected1 = (peerId, heads) => {
-        connected1 = true
+      const onConnected = (peerId, heads) => {
+        replicated = expectedEntryHash && heads.map(e => e.hash).includes(expectedEntryHash)
+      }
+      const onUpdate = (entry) => {
+        replicated = expectedEntryHash && entry.hash === expectedEntryHash
       }
 
-      const onConnected2 = (peerId, heads) => {
-        connected2 = true
-      }
-
-      db1.events.on('join', onConnected1)
-      db2.events.on('join', onConnected2)
+      db2.events.on('join', onConnected)
+      db2.events.on('update', onUpdate)
 
       await db1.addOperation({ op: 'PUT', key: 1, value: 'record 1 on db 1' })
       await db1.addOperation({ op: 'PUT', key: 2, value: 'record 2 on db 1' })
       await db1.addOperation({ op: 'PUT', key: 3, value: 'record 3 on db 1' })
-      await db1.addOperation({ op: 'PUT', key: 4, value: 'record 4 on db 1' })
+      expectedEntryHash = await db1.addOperation({ op: 'PUT', key: 4, value: 'record 4 on db 1' })
 
-      await waitFor(() => connected1, () => true)
-      await waitFor(() => connected2, () => true)
+      await waitFor(() => replicated, () => true)
 
       const all1 = []
       for await (const item of db1.log.iterator()) {
@@ -119,19 +117,19 @@ describe('Database - Replication', function () {
     })
 
     it('replicates databases across two peers with delays', async () => {
-      let connected1 = false
-      let connected2 = false
+      let replicated = false
+      let expectedEntryHash = null
 
-      const onConnected1 = (peerId, heads) => {
-        connected1 = true
+      const onConnected = (peerId, heads) => {
+        replicated = expectedEntryHash && heads.map(e => e.hash).includes(expectedEntryHash)
       }
 
-      const onConnected2 = (peerId, heads) => {
-        connected2 = true
+      const onUpdate = (entry) => {
+        replicated = expectedEntryHash && entry.hash === expectedEntryHash
       }
 
-      db1.events.on('join', onConnected1)
-      db2.events.on('join', onConnected2)
+      db2.events.on('join', onConnected)
+      db2.events.on('update', onUpdate)
 
       await db1.addOperation({ op: 'PUT', key: 1, value: 'record 1 on db 1' })
 
@@ -146,10 +144,9 @@ describe('Database - Replication', function () {
         setTimeout(() => resolve(), 1000)
       })
 
-      await db1.addOperation({ op: 'PUT', key: 4, value: 'record 4 on db 1' })
+      expectedEntryHash = await db1.addOperation({ op: 'PUT', key: 4, value: 'record 4 on db 1' })
 
-      await waitFor(() => connected1, () => true)
-      await waitFor(() => connected2, () => true)
+      await waitFor(() => replicated, () => true)
 
       const all1 = []
       for await (const item of db1.log.iterator()) {
@@ -166,6 +163,7 @@ describe('Database - Replication', function () {
 
     it('adds an operation before db2 is instantiated', async () => {
       let connected = false
+
       const onConnected = (peerId, heads) => {
         connected = true
       }
diff --git a/test/oplog/join.test.js b/test/oplog/join.test.js
index 4dee235..524ce66 100644
--- a/test/oplog/join.test.js
+++ b/test/oplog/join.test.js
@@ -426,4 +426,20 @@ describe('Log - Join', async function () {
     strictEqual(values.length, 10)
     deepStrictEqual(values.map((e) => e.payload), expectedData)
   })
+
+  it('has correct heads after joining logs', async () => {
+    const e1 = await log1.append('hello1')
+    await log1.append('hello2')
+    const e3 = await log1.append('hello3')
+
+    await log2.join(log1)
+
+    const heads1 = await log2.heads()
+    deepStrictEqual(heads1, [e3])
+
+    await log2.joinEntry(e1)
+
+    const heads2 = await log2.heads()
+    deepStrictEqual(heads2, [e3])
+  })
 })
diff --git a/test/oplog/replicate.test.js b/test/oplog/replicate.test.js
index 68aebbb..b3fbd67 100644
--- a/test/oplog/replicate.test.js
+++ b/test/oplog/replicate.test.js
@@ -97,10 +97,10 @@ describe('Log - Replication', function () {
     }
 
     beforeEach(async () => {
-      log1 = await Log(testIdentity1, { logId, storage: storage1 })
-      log2 = await Log(testIdentity2, { logId, storage: storage2 })
-      input1 = await Log(testIdentity1, { logId, storage: storage1 })
-      input2 = await Log(testIdentity2, { logId, storage: storage2 })
+      log1 = await Log(testIdentity1, { logId, entryStorage: storage1 })
+      log2 = await Log(testIdentity2, { logId, entryStorage: storage2 })
+      input1 = await Log(testIdentity1, { logId, entryStorage: storage1 })
+      input2 = await Log(testIdentity2, { logId, entryStorage: storage2 })
       await ipfs1.pubsub.subscribe(logId, handleMessage1)
       await ipfs2.pubsub.subscribe(logId, handleMessage2)
     })
@@ -141,7 +141,7 @@ describe('Log - Replication', function () {
 
       await whileProcessingMessages(config.timeout)
 
-      const result = await Log(testIdentity1, { logId, storage: storage1 })
+      const result = await Log(testIdentity1, { logId, entryStorage: storage1 })
       await result.join(log1)
       await result.join(log2)
 
diff --git a/test/orbitdb-multiple-databases.test.js b/test/orbitdb-multiple-databases.test.js
index 8310617..564a016 100644
--- a/test/orbitdb-multiple-databases.test.js
+++ b/test/orbitdb-multiple-databases.test.js
@@ -157,7 +157,15 @@ describe('orbit-db - Multiple Databases', function () {
     }
 
     // Function to check if all databases have been replicated
-    const allReplicated = () => remoteDatabases.every(isReplicated)
+    const allReplicated = async () => {
+      for (const db of remoteDatabases) {
+        const replicated = await isReplicated(db)
+        if (!replicated) {
+          return false
+        }
+      }
+      return true
+    }
 
     console.log('Waiting for replication to finish')
 
diff --git a/test/sync.test.js b/test/sync.test.js
index 2673c0e..654a716 100644
--- a/test/sync.test.js
+++ b/test/sync.test.js
@@ -142,7 +142,7 @@ describe('Sync protocol', function () {
 
       const onSynced = async (bytes) => {
         syncedHead = await Entry.decode(bytes)
-        log2.joinEntry(syncedHead)
+        await log2.joinEntry(syncedHead)
         syncedEventFired = true
       }
 
@@ -178,16 +178,17 @@ describe('Sync protocol', function () {
       strictEqual(sync1.peers.has(String(peerId2)), true)
     })
 
-    it('eventually reaches consistency', async () => {
+    it('is eventually consistent', async () => {
       await sync1.add(await log1.append('hello2'))
       await sync1.add(await log1.append('hello3'))
       await sync1.add(await log1.append('hello4'))
-      expectedEntry = await log1.append('hello5')
-      await sync1.add(expectedEntry)
+      const expected = await log1.append('hello5')
 
-      await waitFor(() => syncedEventFired, () => true)
+      await sync1.add(expected)
 
-      deepStrictEqual(syncedHead, expectedEntry)
+      await waitFor(() => Entry.isEqual(expected, syncedHead), () => true)
+
+      deepStrictEqual(syncedHead, expected)
 
       deepStrictEqual(await log1.heads(), await log2.heads())
 
@@ -348,8 +349,8 @@ describe('Sync protocol', function () {
       log2 = await Log(testIdentity2, { logId: 'synclog1' })
 
       const onSynced = async (bytes) => {
-        syncedHead = await Entry.decode(bytes)
-        if (expectedEntry) {
+        if (expectedEntry && !syncedEventFired) {
+          syncedHead = await Entry.decode(bytes)
           syncedEventFired = expectedEntry.hash === syncedHead.hash
         }
       }
@@ -491,8 +492,8 @@ describe('Sync protocol', function () {
     let leavingPeerId
 
     before(async () => {
-      const log1 = await Log(testIdentity1, { logId: 'synclog2' })
-      const log2 = await Log(testIdentity2, { logId: 'synclog2' })
+      const log1 = await Log(testIdentity1, { logId: 'synclog3' })
+      const log2 = await Log(testIdentity2, { logId: 'synclog3' })
 
       const onJoin = (peerId, heads) => {
         joinEventFired = true
@@ -511,12 +512,12 @@ describe('Sync protocol', function () {
       }
 
       const onSynced = (bytes) => {
-        throw new Error('Sync Error')
+        sync2.events.emit('error', new Error('Sync Error'))
       }
 
       await log1.append('hello!')
 
-      sync1 = await Sync({ ipfs: ipfs1, log: log1 })
+      sync1 = await Sync({ ipfs: ipfs1, log: log1, onSynced })
       sync2 = await Sync({ ipfs: ipfs2, log: log2, onSynced })
       sync1.events.on('join', onJoin)
       sync1.events.on('leave', onLeave)