diff --git a/coordinator/src/substrate/mod.rs b/coordinator/src/substrate/mod.rs
index 9ee96e52..5508cbe1 100644
--- a/coordinator/src/substrate/mod.rs
+++ b/coordinator/src/substrate/mod.rs
@@ -147,8 +147,6 @@ async fn handle_batch_and_burns<Pro: Processors>(
       network_had_event(&mut burns, &mut batches, network);
 
       // Make sure this is the only Batch event for this network in this Block
-      // TODO: Make sure Serai rejects multiple Batchs within the same block. It should, as of an
-      // yet to be merged branch
       assert!(batch_block.insert(network, network_block).is_none());
 
       // Add the batch included by this block
diff --git a/coordinator/src/tributary/db.rs b/coordinator/src/tributary/db.rs
index acb6e842..9a89139b 100644
--- a/coordinator/src/tributary/db.rs
+++ b/coordinator/src/tributary/db.rs
@@ -17,11 +17,17 @@ pub enum Topic {
 
 impl Topic {
   fn as_key(&self, genesis: [u8; 32]) -> Vec<u8> {
-    match self {
-      Topic::Dkg => [genesis.as_slice(), b"dkg".as_ref()].concat(),
-      Topic::Batch(id) => [genesis.as_slice(), b"batch".as_ref(), id.as_ref()].concat(),
-      Topic::Sign(id) => [genesis.as_slice(), b"sign".as_ref(), id.as_ref()].concat(),
-    }
+    let mut res = genesis.to_vec();
+    let (label, id) = match self {
+      Topic::Dkg => (b"dkg".as_slice(), [].as_slice()),
+      Topic::Batch(id) => (b"batch".as_slice(), id.as_slice()),
+      Topic::Sign(id) => (b"sign".as_slice(), id.as_slice()),
+    };
+    res.push(u8::try_from(label.len()).unwrap());
+    res.extend(label);
+    res.push(u8::try_from(id.len()).unwrap());
+    res.extend(id);
+    res
   }
 }
 
@@ -35,13 +41,12 @@ pub struct DataSpecification {
 
 impl DataSpecification {
   fn as_key(&self, genesis: [u8; 32]) -> Vec<u8> {
-    // TODO: Use a proper transcript here to avoid conflicts?
-    [
-      self.topic.as_key(genesis).as_ref(),
-      self.label.as_bytes(),
-      self.attempt.to_le_bytes().as_ref(),
-    ]
-    .concat()
+    let mut res = self.topic.as_key(genesis);
+    let label_bytes = self.label.bytes();
+    res.push(u8::try_from(label_bytes.len()).unwrap());
+    res.extend(label_bytes);
+    res.extend(self.attempt.to_le_bytes());
+    res
   }
 }
 
diff --git a/coordinator/src/tributary/handle.rs b/coordinator/src/tributary/handle.rs
index 257f6932..a9cc23dc 100644
--- a/coordinator/src/tributary/handle.rs
+++ b/coordinator/src/tributary/handle.rs
@@ -40,9 +40,19 @@ use crate::{
   },
 };
 
+const DKG_COMMITMENTS: &str = "commitments";
+const DKG_SHARES: &str = "shares";
 const DKG_CONFIRMATION_NONCES: &str = "confirmation_nonces";
 const DKG_CONFIRMATION_SHARES: &str = "confirmation_shares";
 
+// These s/b prefixes between Batch and Sign should be unnecessary, as Batch/Share entries
+// themselves should already be domain separated
+const BATCH_PREPROCESS: &str = "b_preprocess";
+const BATCH_SHARE: &str = "b_share";
+
+const SIGN_PREPROCESS: &str = "s_preprocess";
+const SIGN_SHARE: &str = "s_share";
+
 // Instead of maintaing state, this simply re-creates the machine(s) in-full on every call (which
 // should only be once per tributary).
 // This simplifies data flow and prevents requiring multiple paths.
@@ -290,7 +300,7 @@ pub(crate) async fn handle_application_tx<
     Transaction::DkgCommitments(attempt, bytes, signed) => {
       match handle(
         txn,
-        &DataSpecification { topic: Topic::Dkg, label: "commitments", attempt },
+        &DataSpecification { topic: Topic::Dkg, label: DKG_COMMITMENTS, attempt },
         bytes,
         &signed,
       ) {
@@ -345,7 +355,7 @@ pub(crate) async fn handle_application_tx<
       );
       match handle(
         txn,
-        &DataSpecification { topic: Topic::Dkg, label: "shares", attempt },
+        &DataSpecification { topic: Topic::Dkg, label: DKG_SHARES, attempt },
         bytes,
         &signed,
       ) {
@@ -436,7 +446,7 @@ pub(crate) async fn handle_application_tx<
         txn,
         &DataSpecification {
           topic: Topic::Batch(data.plan),
-          label: "preprocess",
+          label: BATCH_PREPROCESS,
           attempt: data.attempt,
         },
         data.data,
@@ -463,7 +473,7 @@ pub(crate) async fn handle_application_tx<
         txn,
         &DataSpecification {
           topic: Topic::Batch(data.plan),
-          label: "share",
+          label: BATCH_SHARE,
           attempt: data.attempt,
         },
         data.data,
@@ -494,7 +504,7 @@ pub(crate) async fn handle_application_tx<
         txn,
         &DataSpecification {
           topic: Topic::Sign(data.plan),
-          label: "preprocess",
+          label: SIGN_PREPROCESS,
           attempt: data.attempt,
         },
         data.data,
@@ -527,7 +537,11 @@ pub(crate) async fn handle_application_tx<
       let key_pair = TributaryDb::<D>::key_pair(txn, spec.set());
       match handle(
         txn,
-        &DataSpecification { topic: Topic::Sign(data.plan), label: "share", attempt: data.attempt },
+        &DataSpecification {
+          topic: Topic::Sign(data.plan),
+          label: SIGN_SHARE,
+          attempt: data.attempt,
+        },
         data.data,
         &data.signed,
       ) {