diff --git a/src/database/iter.rs b/src/database/iter.rs
index bbbab491..4845e977 100644
--- a/src/database/iter.rs
+++ b/src/database/iter.rs
@@ -3,12 +3,14 @@ use std::{iter::FusedIterator, sync::Arc};
 use conduit::Result;
 use rocksdb::{ColumnFamily, DBRawIteratorWithThreadMode, Direction, IteratorMode, ReadOptions};
 
-use crate::{engine::Db, map::KeyVal, result, Engine};
+use crate::{
+	engine::Db,
+	result,
+	slice::{OwnedKeyVal, OwnedKeyValPair},
+	Engine,
+};
 
 type Cursor<'cursor> = DBRawIteratorWithThreadMode<'cursor, Db>;
-type Key<'item> = &'item [u8];
-type Val<'item> = &'item [u8];
-type Item<'item> = (Key<'item>, Val<'item>);
 
 struct State<'cursor> {
 	cursor: Cursor<'cursor>,
@@ -48,7 +50,7 @@ impl<'cursor> Iter<'cursor> {
 }
 
 impl Iterator for Iter<'_> {
-	type Item = KeyVal;
+	type Item = OwnedKeyValPair;
 
 	fn next(&mut self) -> Option<Self::Item> {
 		if !self.state.init && self.state.valid {
@@ -57,10 +59,15 @@ impl Iterator for Iter<'_> {
 			self.state.init = false;
 		}
 
-		self.state.cursor.item().map(into_keyval).or_else(|| {
-			when_invalid(&mut self.state).expect("iterator invalidated due to error");
-			None
-		})
+		self.state
+			.cursor
+			.item()
+			.map(OwnedKeyVal::from)
+			.map(OwnedKeyVal::to_tuple)
+			.or_else(|| {
+				when_invalid(&mut self.state).expect("iterator invalidated due to error");
+				None
+			})
 	}
 }
 
@@ -101,5 +108,3 @@ fn into_direction(mode: &IteratorMode<'_>) -> Direction {
 		End | From(_, Reverse) => Reverse,
 	}
 }
-
-fn into_keyval((key, val): Item<'_>) -> KeyVal { (Vec::from(key), Vec::from(val)) }
diff --git a/src/database/map.rs b/src/database/map.rs
index f7b16b7e..73cf5107 100644
--- a/src/database/map.rs
+++ b/src/database/map.rs
@@ -1,11 +1,16 @@
-use std::{future::Future, pin::Pin, sync::Arc};
+use std::{future::Future, mem::size_of, pin::Pin, sync::Arc};
 
 use conduit::{utils, Result};
 use rocksdb::{
 	AsColumnFamilyRef, ColumnFamily, Direction, IteratorMode, ReadOptions, WriteBatchWithTransaction, WriteOptions,
 };
 
-use crate::{or_else, result, watchers::Watchers, Engine, Handle, Iter};
+use crate::{
+	or_else, result,
+	slice::{Byte, Key, KeyVal, OwnedKey, OwnedKeyValPair, OwnedVal, Val},
+	watchers::Watchers,
+	Engine, Handle, Iter,
+};
 
 pub struct Map {
 	name: String,
@@ -16,9 +21,7 @@ pub struct Map {
 	read_options: ReadOptions,
 }
 
-pub(crate) type KeyVal = (Key, Val);
-pub(crate) type Val = Vec<u8>;
-pub(crate) type Key = Vec<u8>;
+type OwnedKeyValPairIter<'a> = Box<dyn Iterator<Item = OwnedKeyValPair> + Send + 'a>;
 
 impl Map {
 	pub(crate) fn open(db: &Arc<Engine>, name: &str) -> Result<Arc<Self>> {
@@ -32,19 +35,19 @@ impl Map {
 		}))
 	}
 
-	pub fn get(&self, key: &[u8]) -> Result<Option<Handle<'_>>> {
+	pub fn get(&self, key: &Key) -> Result<Option<Handle<'_>>> {
 		let read_options = &self.read_options;
 		let res = self.db.db.get_pinned_cf_opt(&self.cf(), key, read_options);
 
 		Ok(result(res)?.map(Handle::from))
 	}
 
-	pub fn multi_get(&self, keys: &[&[u8]]) -> Result<Vec<Option<Vec<u8>>>> {
+	pub fn multi_get(&self, keys: &[&Key]) -> Result<Vec<Option<OwnedVal>>> {
 		// Optimization can be `true` if key vector is pre-sorted **by the column
 		// comparator**.
 		const SORTED: bool = false;
 
-		let mut ret: Vec<Option<Vec<u8>>> = Vec::with_capacity(keys.len());
+		let mut ret: Vec<Option<OwnedKey>> = Vec::with_capacity(keys.len());
 		let read_options = &self.read_options;
 		for res in self
 			.db
@@ -61,7 +64,7 @@ impl Map {
 		Ok(ret)
 	}
 
-	pub fn insert(&self, key: &[u8], value: &[u8]) -> Result<()> {
+	pub fn insert(&self, key: &Key, value: &Val) -> Result<()> {
 		let write_options = &self.write_options;
 		self.db
 			.db
@@ -77,9 +80,12 @@ impl Map {
 		Ok(())
 	}
 
-	pub fn insert_batch(&self, iter: &mut dyn Iterator<Item = KeyVal>) -> Result<()> {
+	pub fn insert_batch<'a, I>(&'a self, iter: I) -> Result<()>
+	where
+		I: Iterator<Item = KeyVal<'a>>,
+	{
 		let mut batch = WriteBatchWithTransaction::<false>::default();
-		for (key, value) in iter {
+		for KeyVal(key, value) in iter {
 			batch.put_cf(&self.cf(), key, value);
 		}
 
@@ -93,7 +99,7 @@ impl Map {
 		result(res)
 	}
 
-	pub fn remove(&self, key: &[u8]) -> Result<()> {
+	pub fn remove(&self, key: &Key) -> Result<()> {
 		let write_options = &self.write_options;
 		let res = self.db.db.delete_cf_opt(&self.cf(), key, write_options);
 
@@ -104,7 +110,10 @@ impl Map {
 		result(res)
 	}
 
-	pub fn remove_batch(&self, iter: &mut dyn Iterator<Item = Key>) -> Result<()> {
+	pub fn remove_batch<'a, I>(&'a self, iter: I) -> Result<()>
+	where
+		I: Iterator<Item = &'a Key>,
+	{
 		let mut batch = WriteBatchWithTransaction::<false>::default();
 		for key in iter {
 			batch.delete_cf(&self.cf(), key);
@@ -120,14 +129,14 @@ impl Map {
 		result(res)
 	}
 
-	pub fn iter<'a>(&'a self) -> Box<dyn Iterator<Item = KeyVal> + 'a> {
+	pub fn iter(&self) -> OwnedKeyValPairIter<'_> {
 		let mode = IteratorMode::Start;
 		let read_options = read_options_default();
 		Box::new(Iter::new(&self.db, &self.cf, read_options, &mode))
 	}
 
-	pub fn iter_from<'a>(&'a self, from: &[u8], backwards: bool) -> Box<dyn Iterator<Item = KeyVal> + 'a> {
-		let direction = if backwards {
+	pub fn iter_from(&self, from: &Key, reverse: bool) -> OwnedKeyValPairIter<'_> {
+		let direction = if reverse {
 			Direction::Reverse
 		} else {
 			Direction::Forward
@@ -137,13 +146,13 @@ impl Map {
 		Box::new(Iter::new(&self.db, &self.cf, read_options, &mode))
 	}
 
-	pub fn scan_prefix<'a>(&'a self, prefix: Vec<u8>) -> Box<dyn Iterator<Item = KeyVal> + 'a> {
+	pub fn scan_prefix(&self, prefix: OwnedKey) -> OwnedKeyValPairIter<'_> {
 		let mode = IteratorMode::From(&prefix, Direction::Forward);
 		let read_options = read_options_default();
 		Box::new(Iter::new(&self.db, &self.cf, read_options, &mode).take_while(move |(k, _)| k.starts_with(&prefix)))
 	}
 
-	pub fn increment(&self, key: &[u8]) -> Result<[u8; 8]> {
+	pub fn increment(&self, key: &Key) -> Result<[Byte; size_of::<u64>()]> {
 		let old = self.get(key)?;
 		let new = utils::increment(old.as_deref());
 		self.insert(key, &new)?;
@@ -155,10 +164,13 @@ impl Map {
 		Ok(new)
 	}
 
-	pub fn increment_batch(&self, iter: &mut dyn Iterator<Item = Val>) -> Result<()> {
+	pub fn increment_batch<'a, I>(&'a self, iter: I) -> Result<()>
+	where
+		I: Iterator<Item = &'a Key>,
+	{
 		let mut batch = WriteBatchWithTransaction::<false>::default();
 		for key in iter {
-			let old = self.get(&key)?;
+			let old = self.get(key)?;
 			let new = utils::increment(old.as_deref());
 			batch.put_cf(&self.cf(), key, new);
 		}
@@ -173,7 +185,7 @@ impl Map {
 		result(res)
 	}
 
-	pub fn watch_prefix<'a>(&'a self, prefix: &[u8]) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>> {
+	pub fn watch_prefix<'a>(&'a self, prefix: &Key) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>> {
 		self.watchers.watch(prefix)
 	}
 
@@ -184,8 +196,8 @@ impl Map {
 }
 
 impl<'a> IntoIterator for &'a Map {
-	type IntoIter = Box<dyn Iterator<Item = Self::Item> + 'a>;
-	type Item = KeyVal;
+	type IntoIter = Box<dyn Iterator<Item = Self::Item> + Send + 'a>;
+	type Item = OwnedKeyValPair;
 
 	fn into_iter(self) -> Self::IntoIter { self.iter() }
 }
diff --git a/src/database/mod.rs b/src/database/mod.rs
index 39566896..283224f6 100644
--- a/src/database/mod.rs
+++ b/src/database/mod.rs
@@ -6,6 +6,7 @@ mod iter;
 mod map;
 pub mod maps;
 mod opts;
+mod slice;
 mod util;
 mod watchers;
 
@@ -17,6 +18,7 @@ pub(crate) use engine::Engine;
 pub use handle::Handle;
 pub use iter::Iter;
 pub use map::Map;
+pub use slice::{Key, KeyVal, OwnedKey, OwnedKeyVal, OwnedVal, Val};
 pub(crate) use util::{or_else, result};
 
 conduit::mod_ctor! {}
diff --git a/src/database/slice.rs b/src/database/slice.rs
new file mode 100644
index 00000000..770f1957
--- /dev/null
+++ b/src/database/slice.rs
@@ -0,0 +1,64 @@
+pub struct OwnedKeyVal(pub OwnedKey, pub OwnedVal);
+pub(crate) type OwnedKeyValPair = (OwnedKey, OwnedVal);
+pub type OwnedVal = Vec<Byte>;
+pub type OwnedKey = Vec<Byte>;
+
+pub struct KeyVal<'item>(pub &'item Key, pub &'item Val);
+pub(crate) type KeyValPair<'item> = (&'item Key, &'item Val);
+pub type Val = [Byte];
+pub type Key = [Byte];
+
+pub(crate) type Byte = u8;
+
+impl OwnedKeyVal {
+	#[inline]
+	#[must_use]
+	pub fn as_slice(&self) -> KeyVal<'_> { KeyVal(&self.0, &self.1) }
+
+	#[inline]
+	#[must_use]
+	pub fn to_tuple(self) -> OwnedKeyValPair { (self.0, self.1) }
+}
+
+impl From<OwnedKeyValPair> for OwnedKeyVal {
+	#[inline]
+	fn from((key, val): OwnedKeyValPair) -> Self { Self(key, val) }
+}
+
+impl From<&KeyVal<'_>> for OwnedKeyVal {
+	fn from(slice: &KeyVal<'_>) -> Self { slice.to_owned() }
+}
+
+impl From<KeyValPair<'_>> for OwnedKeyVal {
+	fn from((key, val): KeyValPair<'_>) -> Self { Self(Vec::from(key), Vec::from(val)) }
+}
+
+impl From<OwnedKeyVal> for OwnedKeyValPair {
+	#[inline]
+	fn from(val: OwnedKeyVal) -> Self { val.to_tuple() }
+}
+
+impl KeyVal<'_> {
+	#[inline]
+	#[must_use]
+	pub fn to_owned(&self) -> OwnedKeyVal { OwnedKeyVal::from(self) }
+
+	#[inline]
+	#[must_use]
+	pub fn as_tuple(&self) -> KeyValPair<'_> { (self.0, self.1) }
+}
+
+impl<'a> From<&'a OwnedKeyVal> for KeyVal<'a> {
+	#[inline]
+	fn from(owned: &'a OwnedKeyVal) -> Self { owned.as_slice() }
+}
+
+impl<'a> From<&'a OwnedKeyValPair> for KeyVal<'a> {
+	#[inline]
+	fn from((key, val): &'a OwnedKeyValPair) -> Self { KeyVal(key.as_slice(), val.as_slice()) }
+}
+
+impl<'a> From<KeyValPair<'a>> for KeyVal<'a> {
+	#[inline]
+	fn from((key, val): KeyValPair<'a>) -> Self { KeyVal(key, val) }
+}
diff --git a/src/service/globals/migrations.rs b/src/service/globals/migrations.rs
index 4109017d..a98eec4e 100644
--- a/src/service/globals/migrations.rs
+++ b/src/service/globals/migrations.rs
@@ -466,47 +466,53 @@ async fn db_lt_8(db: &Arc<Database>, _config: &Config) -> Result<()> {
 		info!("Migration: 8");
 	}
 	// Update pduids db layout
-	let mut batch = pduid_pdu.iter().filter_map(|(key, v)| {
-		if !key.starts_with(b"!") {
-			return None;
-		}
-		let mut parts = key.splitn(2, |&b| b == 0xFF);
-		let room_id = parts.next().unwrap();
-		let count = parts.next().unwrap();
+	let batch = pduid_pdu
+		.iter()
+		.filter_map(|(key, v)| {
+			if !key.starts_with(b"!") {
+				return None;
+			}
+			let mut parts = key.splitn(2, |&b| b == 0xFF);
+			let room_id = parts.next().unwrap();
+			let count = parts.next().unwrap();
 
-		let short_room_id = roomid_shortroomid
-			.get(room_id)
-			.unwrap()
-			.expect("shortroomid should exist");
+			let short_room_id = roomid_shortroomid
+				.get(room_id)
+				.unwrap()
+				.expect("shortroomid should exist");
 
-		let mut new_key = short_room_id.to_vec();
-		new_key.extend_from_slice(count);
+			let mut new_key = short_room_id.to_vec();
+			new_key.extend_from_slice(count);
 
-		Some((new_key, v))
-	});
+			Some(database::OwnedKeyVal(new_key, v))
+		})
+		.collect::<Vec<_>>();
 
-	pduid_pdu.insert_batch(&mut batch)?;
+	pduid_pdu.insert_batch(batch.iter().map(database::KeyVal::from))?;
 
-	let mut batch2 = eventid_pduid.iter().filter_map(|(k, value)| {
-		if !value.starts_with(b"!") {
-			return None;
-		}
-		let mut parts = value.splitn(2, |&b| b == 0xFF);
-		let room_id = parts.next().unwrap();
-		let count = parts.next().unwrap();
+	let batch2 = eventid_pduid
+		.iter()
+		.filter_map(|(k, value)| {
+			if !value.starts_with(b"!") {
+				return None;
+			}
+			let mut parts = value.splitn(2, |&b| b == 0xFF);
+			let room_id = parts.next().unwrap();
+			let count = parts.next().unwrap();
 
-		let short_room_id = roomid_shortroomid
-			.get(room_id)
-			.unwrap()
-			.expect("shortroomid should exist");
+			let short_room_id = roomid_shortroomid
+				.get(room_id)
+				.unwrap()
+				.expect("shortroomid should exist");
 
-		let mut new_value = short_room_id.to_vec();
-		new_value.extend_from_slice(count);
+			let mut new_value = short_room_id.to_vec();
+			new_value.extend_from_slice(count);
 
-		Some((k, new_value))
-	});
+			Some(database::OwnedKeyVal(k, new_value))
+		})
+		.collect::<Vec<_>>();
 
-	eventid_pduid.insert_batch(&mut batch2)?;
+	eventid_pduid.insert_batch(batch2.iter().map(database::KeyVal::from))?;
 
 	services().globals.bump_database_version(8)?;
 	info!("Migration: 7 -> 8 finished");
@@ -538,12 +544,13 @@ async fn db_lt_9(db: &Arc<Database>, _config: &Config) -> Result<()> {
 			new_key.extend_from_slice(word);
 			new_key.push(0xFF);
 			new_key.extend_from_slice(pdu_id_count);
-			Some((new_key, Vec::new()))
+			Some(database::OwnedKeyVal(new_key, Vec::<u8>::new()))
 		})
 		.peekable();
 
 	while iter.peek().is_some() {
-		tokenids.insert_batch(&mut iter.by_ref().take(1000))?;
+		let batch = iter.by_ref().take(1000).collect::<Vec<_>>();
+		tokenids.insert_batch(batch.iter().map(database::KeyVal::from))?;
 		debug!("Inserted smaller batch");
 	}
 
diff --git a/src/service/rooms/search/data.rs b/src/service/rooms/search/data.rs
index fe5d3edf..79b23cba 100644
--- a/src/service/rooms/search/data.rs
+++ b/src/service/rooms/search/data.rs
@@ -20,15 +20,18 @@ impl Data {
 	}
 
 	pub(super) fn index_pdu(&self, shortroomid: u64, pdu_id: &[u8], message_body: &str) -> Result<()> {
-		let mut batch = tokenize(message_body).map(|word| {
-			let mut key = shortroomid.to_be_bytes().to_vec();
-			key.extend_from_slice(word.as_bytes());
-			key.push(0xFF);
-			key.extend_from_slice(pdu_id); // TODO: currently we save the room id a second time here
-			(key, Vec::new())
-		});
+		let batch = tokenize(message_body)
+			.map(|word| {
+				let mut key = shortroomid.to_be_bytes().to_vec();
+				key.extend_from_slice(word.as_bytes());
+				key.push(0xFF);
+				key.extend_from_slice(pdu_id); // TODO: currently we save the room id a second time here
+				(key, Vec::<u8>::new())
+			})
+			.collect::<Vec<_>>();
 
-		self.tokenids.insert_batch(&mut batch)
+		self.tokenids
+			.insert_batch(batch.iter().map(database::KeyVal::from))
 	}
 
 	pub(super) fn deindex_pdu(&self, shortroomid: u64, pdu_id: &[u8], message_body: &str) -> Result<()> {
diff --git a/src/service/rooms/timeline/data.rs b/src/service/rooms/timeline/data.rs
index 6609bde8..023457fa 100644
--- a/src/service/rooms/timeline/data.rs
+++ b/src/service/rooms/timeline/data.rs
@@ -268,9 +268,9 @@ impl Data {
 		}
 
 		self.userroomid_notificationcount
-			.increment_batch(&mut notifies_batch.into_iter())?;
+			.increment_batch(notifies_batch.iter().map(Vec::as_slice))?;
 		self.userroomid_highlightcount
-			.increment_batch(&mut highlights_batch.into_iter())?;
+			.increment_batch(highlights_batch.iter().map(Vec::as_slice))?;
 		Ok(())
 	}
 }
diff --git a/src/service/sending/data.rs b/src/service/sending/data.rs
index 20e5b77a..22b69818 100644
--- a/src/service/sending/data.rs
+++ b/src/service/sending/data.rs
@@ -87,7 +87,7 @@ impl Data {
 			keys.push(key);
 		}
 		self.servernameevent_data
-			.insert_batch(&mut batch.into_iter())?;
+			.insert_batch(batch.iter().map(database::KeyVal::from))?;
 		Ok(keys)
 	}