# Begin Block At the start of each block, atomic swaps that meet certain criteria are expired or deleted. ```go func BeginBlocker(ctx sdk.Context, k Keeper) { k.UpdateExpiredAtomicSwaps(ctx) k.DeleteClosedAtomicSwapsFromLongtermStorage(ctx) } ``` ## Expiration If an atomic swap's `ExpireHeight` is greater than the current block height, it will be expired. The logic to expire atomic swaps is as follows: ```go var expiredSwapIDs []string k.IterateAtomicSwapsByBlock(ctx, uint64(ctx.BlockHeight()), func(id []byte) bool { atomicSwap, found := k.GetAtomicSwap(ctx, id) if !found { return false } // Expire the uncompleted swap and update both indexes atomicSwap.Status = types.Expired k.RemoveFromByBlockIndex(ctx, atomicSwap) k.SetAtomicSwap(ctx, atomicSwap) expiredSwapIDs = append(expiredSwapIDs, hex.EncodeToString(atomicSwap.GetSwapID())) return false }) ``` ## Deletion Atomic swaps are deleted 86400 blocks (one week, assuming a block time of 7 seconds) after being completed. The logic to delete atomic swaps is as follows: ```go k.IterateAtomicSwapsLongtermStorage(ctx, uint64(ctx.BlockHeight()), func(id []byte) bool { swap, found := k.GetAtomicSwap(ctx, id) if !found { return false } k.RemoveAtomicSwap(ctx, swap.GetSwapID()) k.RemoveFromLongtermStorage(ctx, swap) return false }) ```