diff --git a/storage/blockchain/src/ops/alt_block.rs b/storage/blockchain/src/ops/alt_block.rs
new file mode 100644
index 00000000..d04899ef
--- /dev/null
+++ b/storage/blockchain/src/ops/alt_block.rs
@@ -0,0 +1,104 @@
+use bytemuck::TransparentWrapper;
+
+use cuprate_database::{DatabaseRw, RuntimeError, StorableVec, DatabaseRo};
+use cuprate_helper::map::split_u128_into_low_high_bits;
+use cuprate_types::{AltBlockInformation, Chain, VerifiedTransactionInformation};
+
+use crate::{
+    tables::TablesMut,
+    types::{AltBlockHeight, AltChainInfo, AltTransactionInfo, BlockHash, CompactAltBlockInfo},
+};
+
+pub fn add_alt_block(
+    alt_block: &AltBlockInformation,
+    tables: &mut impl TablesMut,
+) -> Result<(), RuntimeError> {
+    let alt_block_height = AltBlockHeight {
+        chain_id: alt_block.chain_id.into(),
+        height: alt_block.height,
+    };
+
+    tables
+        .alt_block_heights_mut()
+        .put(&alt_block.block_hash, &alt_block_height)?;
+
+    check_add_alt_chain_info(&alt_block_height, &alt_block.block.header.previous, tables)?;
+
+    let (cumulative_difficulty_low, cumulative_difficulty_high) =
+        split_u128_into_low_high_bits(alt_block.cumulative_difficulty);
+
+    let alt_block_info = CompactAltBlockInfo {
+        block_hash: alt_block.block_hash,
+        pow_hash: alt_block.pow_hash,
+        height: alt_block.height,
+        weight: alt_block.weight,
+        long_term_weight: alt_block.long_term_weight,
+        cumulative_difficulty_low,
+        cumulative_difficulty_high,
+    };
+
+    tables
+        .alt_blocks_info_mut()
+        .put(&alt_block_height, &alt_block_info)?;
+
+    tables.alt_block_blobs_mut().put(
+        &alt_block_height,
+        StorableVec::wrap_ref(&alt_block.block_blob),
+    )?;
+
+    for tx in &alt_block.txs {
+        add_alt_transaction(&tx, tables)?;
+    }
+
+    Ok(())
+}
+
+pub fn add_alt_transaction(
+    tx: &VerifiedTransactionInformation,
+    tables: &mut impl TablesMut,
+) -> Result<(), RuntimeError> {
+    if tables.tx_ids().get(&tx.tx_hash).is_ok()
+        || tables.alt_transaction_infos().get(&tx.tx_hash).is_ok()
+    {
+        return Ok(());
+    }
+
+    tables.alt_transaction_infos_mut().put(
+        &tx.tx_hash,
+        &AltTransactionInfo {
+            tx_weight: tx.tx_weight,
+            fee: tx.fee,
+            tx_hash: tx.tx_hash,
+        },
+    )?;
+
+    tables
+        .alt_transaction_blobs_mut()
+        .put(&tx.tx_hash, StorableVec::wrap_ref(&tx.tx_blob))
+}
+
+pub fn check_add_alt_chain_info(
+    alt_block_height: &AltBlockHeight,
+    prev_hash: &BlockHash,
+    tables: &mut impl TablesMut,
+) -> Result<(), RuntimeError> {
+    match tables.alt_chain_infos().get(&alt_block_height.chain_id) {
+        Ok(_) => return Ok(()),
+        Err(RuntimeError::KeyNotFound) => (),
+        Err(e) => return Err(e),
+    }
+
+    let parent_chain = match tables.alt_block_heights().get(prev_hash) {
+        Ok(alt_parent_height) => Chain::Alt(alt_parent_height.chain_id.into()),
+        Err(RuntimeError::KeyNotFound) => Chain::Main,
+        Err(e) => return Err(e),
+    };
+
+    tables.alt_chain_infos_mut().put(
+        &alt_block_height.chain_id,
+        &AltChainInfo {
+            parent_chain: parent_chain.into(),
+            common_ancestor_height: alt_block_height.height - 1,
+        },
+    )
+}
diff --git a/storage/blockchain/src/ops/mod.rs b/storage/blockchain/src/ops/mod.rs
index 4ff7dff1..1ec9c237 100644
--- a/storage/blockchain/src/ops/mod.rs
+++ b/storage/blockchain/src/ops/mod.rs
@@ -108,5 +108,6 @@ pub mod key_image;
 pub mod output;
 pub mod property;
 pub mod tx;
+pub mod alt_block;
 
 mod macros;
diff --git a/storage/blockchain/src/tables.rs b/storage/blockchain/src/tables.rs
index 6db76816..381430d7 100644
--- a/storage/blockchain/src/tables.rs
+++ b/storage/blockchain/src/tables.rs
@@ -16,7 +16,12 @@
 //! accessing _all_ tables defined here at once.
 
 //---------------------------------------------------------------------------------------------------- Import
-use crate::types::{Amount, AmountIndex, AmountIndices, BlockBlob, BlockHash, BlockHeight, BlockInfo, KeyImage, Output, PreRctOutputId, PrunableBlob, PrunableHash, PrunedBlob, RctOutput, TxBlob, TxHash, TxId, UnlockTime, RawChainId, AltChainInfo, AltBlockHeight, CompactAltBlockInfo, AltTransactionInfo};
+use crate::types::{
+    AltBlockHeight, AltChainInfo, AltTransactionInfo, Amount, AmountIndex, AmountIndices,
+    BlockBlob, BlockHash, BlockHeight, BlockInfo, CompactAltBlockInfo, KeyImage, Output,
+    PreRctOutputId, PrunableBlob, PrunableHash, PrunedBlob, RawChainId, RctOutput, TxBlob, TxHash,
+    TxId, UnlockTime,
+};
 
 //---------------------------------------------------------------------------------------------------- Tables
 // Notes:
diff --git a/storage/blockchain/src/types.rs b/storage/blockchain/src/types.rs
index 73c7614f..88ece10b 100644
--- a/storage/blockchain/src/types.rs
+++ b/storage/blockchain/src/types.rs
@@ -348,6 +348,14 @@ impl From<RawChain> for Chain {
     }
 }
 
+impl From<RawChainId> for RawChain {
+    fn from(value: RawChainId) -> Self {
+        assert_ne!(value.0, 0);
+
+        RawChain(value.0)
+    }
+}
+
 //---------------------------------------------------------------------------------------------------- RawChainId
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, Ord, Hash, Pod, Zeroable)]
 #[repr(transparent)]
@@ -371,16 +379,16 @@ impl Key for RawChainId {}
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, Ord, Hash, Pod, Zeroable)]
 #[repr(C)]
 pub struct AltChainInfo {
-    parent_chain: RawChain,
-    common_ancestor_height: u64
+    pub parent_chain: RawChain,
+    pub common_ancestor_height: usize,
 }
 
 //---------------------------------------------------------------------------------------------------- AltBlockHeight
 #[derive(Copy, Clone, Debug, PartialEq, PartialOrd, Eq, Ord, Hash, Pod, Zeroable)]
 #[repr(C)]
 pub struct AltBlockHeight {
-    chain_id: u64,
-    height: u64,
+    pub chain_id: RawChainId,
+    pub height: usize,
 }
 
 impl Key for AltBlockHeight {}
@@ -396,7 +404,7 @@ pub struct CompactAltBlockInfo {
     /// The block's proof-of-work hash.
     pub pow_hash: [u8; 32],
     /// The block's height.
-    pub height: u64,
+    pub height: usize,
     /// The adjusted block size, in bytes.
     pub weight: usize,
     /// The long term block weight, which is the weight factored in with previous block weights.
@@ -404,7 +412,6 @@ pub struct CompactAltBlockInfo {
     /// The cumulative difficulty of all blocks up until and including this block.
     pub cumulative_difficulty_low: u64,
     pub cumulative_difficulty_high: u64,
-
 }
 
 //---------------------------------------------------------------------------------------------------- AltTransactionInfo