diff --git a/src/cmd_line.rs b/src/cmd_line.rs
index 1856ca5..0770d5f 100644
--- a/src/cmd_line.rs
+++ b/src/cmd_line.rs
@@ -310,6 +310,7 @@ pub fn run_cmd_line() {
 			|| (cur_state == InstState::Editing && timed_update_ready)
 		{
 			let s = status.get();
+			// TODO: Update duration format? e.g. 1m 42s remaining
 			print_progress(s.blocks_done, s.blocks_total,
 				querying_start, editing_start);
 			last_update = now;
diff --git a/src/commands/clone.rs b/src/commands/clone.rs
index 58985ba..0cb0eeb 100644
--- a/src/commands/clone.rs
+++ b/src/commands/clone.rs
@@ -9,6 +9,9 @@ use crate::utils::query_keys;
 use crate::time_keeper::TimeKeeper;
 
 
+// TODO: This and overlay--cache mapblocks in deserialized form.
+
+
 fn clone(inst: &mut InstBundle) {
 	let src_area = inst.args.area.unwrap();
 	let offset = inst.args.offset.unwrap();
diff --git a/src/commands/vacuum.rs b/src/commands/vacuum.rs
index 961eb5b..dcf7fff 100644
--- a/src/commands/vacuum.rs
+++ b/src/commands/vacuum.rs
@@ -9,6 +9,7 @@ fn vacuum(inst: &mut InstBundle) {
 	inst.status.log_info("Starting vacuum.");
 	let start = Instant::now();
 
+	// TODO: Show simple timer in main thread.
 	match inst.db.vacuum() {
 		Ok(_) => {
 			let time = fmt_duration(start.elapsed());
diff --git a/src/map_block/map_block.rs b/src/map_block/map_block.rs
index 455d984..221afdb 100644
--- a/src/map_block/map_block.rs
+++ b/src/map_block/map_block.rs
@@ -81,6 +81,7 @@ impl MapBlock {
 	}
 
 	pub fn serialize(&self) -> Vec<u8> {
+		// TODO: Use a bigger buffer (unsafe?) to reduce heap allocations.
 		let mut buf = Vec::with_capacity(BLOCK_BUF_SIZE);
 		let mut data = Cursor::new(buf);
 
diff --git a/src/utils.rs b/src/utils.rs
index 94e9f58..2eaf4b0 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -11,6 +11,7 @@ use crate::spatial::{Area, Vec3};
 pub fn query_keys(
 	db: &mut MapDatabase,
 	status: &StatusServer,
+	// TODO: Allow multiple names for setmetavar and replaceininv.
 	search_str: Option<&[u8]>,
 	area: Option<Area>,
 	invert: bool,
diff --git a/todo.md b/todo.md
deleted file mode 100644
index 90c3b6f..0000000
--- a/todo.md
+++ /dev/null
@@ -1,10 +0,0 @@
-Optimizations:
-
-- Cache deserialized map blocks instead of deserializing each time.
-- Overlay: Iterate map blocks in space-filling curve shape to optimize cache usefulness.
-- (DONE) Don't re-compress node data/metadata if it isn't changed.
-- MapBlock::serialize: Use a big buffer somewhere to avoid heap allocations.
-
-Todo?
-
-- Fold area utility functions into the area struct.
\ No newline at end of file