diff --git a/src/dexorder/bin/finaldata.py b/src/dexorder/bin/finaldata.py
index be0271c..95a26af 100644
--- a/src/dexorder/bin/finaldata.py
+++ b/src/dexorder/bin/finaldata.py
@@ -50,7 +50,7 @@ async def main():
     if config.ohlc_dir is None:
         fatal('an ohlc_dir must be configured')
     await blockchain.connect()
-    walker = BlockWalker(flush_callback, timedelta(minutes=5))
+    walker = BlockWalker(flush_callback, timedelta(seconds=config.walker_flush_interval))
     walker.add_event_trigger(handle_backfill_uniswap_swaps,
                              get_contract_event('IUniswapV3PoolEvents', 'Swap'), multi=True)
     await walker.run()
diff --git a/src/dexorder/configuration/schema.py b/src/dexorder/configuration/schema.py
index 603dd3a..172d509 100644
--- a/src/dexorder/configuration/schema.py
+++ b/src/dexorder/configuration/schema.py
@@ -29,4 +29,4 @@ class Config:
     deployments: Optional[dict[str,str]] = field(default_factory=dict)
     min_gas: str = '0'
 
-    tokens_dir: str = '.'
+    walker_flush_interval: float = 300
diff --git a/src/dexorder/ohlc.py b/src/dexorder/ohlc.py
index fc094e6..632e63c 100644
--- a/src/dexorder/ohlc.py
+++ b/src/dexorder/ohlc.py
@@ -1,4 +1,3 @@
-import json
 import logging
 import os
 from datetime import datetime, timedelta, timezone
@@ -11,6 +10,7 @@ from dexorder.base.chain import current_chain
 from dexorder.blockstate import BlockDict, DiffItem, current_blockstate
 from dexorder.blockstate.diff import DiffEntryItem
 from dexorder.database.model import Block
+from dexorder.util import json
 from dexorder.util.shutdown import fatal
 
 log = logging.getLogger(__name__)
diff --git a/src/dexorder/util/json.py b/src/dexorder/util/json.py
index d1895b0..fccfbdc 100644
--- a/src/dexorder/util/json.py
+++ b/src/dexorder/util/json.py
@@ -23,11 +23,21 @@ def _serialize(v):
     raise TypeError
 
 
+def load(file) -> Any:
+    return loads(file.read())
+
 def loads(s):
     return orjson.loads(s)
 
+def dump(obj, file):
+    file.write(dumps(obj))
+
 def dumps(obj):
-    return orjson.dumps(obj, default=_serialize, option=orjson.OPT_PASSTHROUGH_SUBCLASS).decode('utf8')
+    return dumpb(obj).decode('utf8')
+
+def dumpb(obj):
+    opts = orjson.OPT_PASSTHROUGH_SUBCLASS | orjson.OPT_STRICT_INTEGER
+    return orjson.dumps(obj, default=_serialize, option=opts)
 
 
 class JsonEncoder (JSONEncoder):