diff --git a/src/timebin/cached/reader.rs b/src/timebin/cached/reader.rs
index 7b3bf7f..67fa5a4 100644
--- a/src/timebin/cached/reader.rs
+++ b/src/timebin/cached/reader.rs
@@ -24,6 +24,7 @@ autoerr::create_error_v1!(
         ChannelSend,
         ChannelRecv,
         Scylla(String),
+        PrebinnedPartitioningInvalid,
     },
 );
 
@@ -33,12 +34,35 @@ pub type BinsReadResErr = streams::timebin::cached::reader::Error;
 pub type BinsReadRes = Result<Option<BinsBoxed>, BinsReadResErr>;
 pub type BinsReadFutBoxed = Pin<Box<dyn Future<Output = BinsReadRes> + Send>>;
 
-pub fn off_max() -> u64 {
-    1000
+pub enum PrebinnedPartitioning {
+    Sec1,
+    Sec10,
+    Min1,
+    Min10,
+    Hour1,
 }
 
-pub fn part_len(bin_len: DtMs) -> DtMs {
-    DtMs::from_ms_u64(bin_len.ms() * off_max())
+impl PrebinnedPartitioning {
+    pub fn msp_div(&self) -> DtMs {
+        use PrebinnedPartitioning::*;
+        match self {
+            Sec1 => DtMs::from_ms_u64(1000 * 60 * 10),
+            Sec10 => DtMs::from_ms_u64(1000 * 60 * 60 * 2),
+            Min1 => DtMs::from_ms_u64(1000 * 60 * 60 * 8),
+            Min10 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 4),
+            Hour1 => DtMs::from_ms_u64(1000 * 60 * 60 * 24 * 28),
+        }
+    }
+}
+
+impl TryFrom<DtMs> for PrebinnedPartitioning {
+    type Error = Error;
+
+    fn try_from(value: DtMs) -> Result<Self, Self::Error> {
+        match value {
+            _ => Err(Error::PrebinnedPartitioningInvalid),
+        }
+    }
 }
 
 pub struct EventsReading {
@@ -179,18 +203,26 @@ impl Stream for CachedReader {
                 }
             } else {
                 if self.ts1next < self.range.nano_end() {
-                    let div = part_len(self.bin_len).ns();
-                    let msp = self.ts1next.ns() / div;
-                    let off = (self.ts1next.ns() - div * msp) / self.bin_len.ns();
-                    let off2 = (self.range.nano_end().ns() - div * msp) / self.bin_len.ns();
-                    let off2 = off2.min(off_max());
-                    self.ts1next = TsNano::from_ns(self.bin_len.ns() * off2 + div * msp);
-                    let offs = off as u32..off2 as u32;
-                    let fut = self
-                        .cache_read_provider
-                        .read(self.series, self.bin_len, msp, offs);
-                    self.reading = Some(Box::pin(fut));
-                    continue;
+                    match PrebinnedPartitioning::try_from(self.range.bin_len_dt_ms()) {
+                        Ok(partt) => {
+                            let binlen = self.bin_len.ns();
+                            let div = partt.msp_div().ns();
+                            let msp = self.ts1next.ns() / div;
+                            let off1 = (self.ts1next.ns() - div * msp) / binlen;
+                            let off2 = (self.range.nano_end().ns() - div * msp) / binlen;
+                            self.ts1next = TsNano::from_ns(binlen * off2 + div * msp);
+                            let offs = off1 as u32..off2 as u32;
+                            let fut =
+                                self.cache_read_provider
+                                    .read(self.series, self.bin_len, msp, offs);
+                            self.reading = Some(Box::pin(fut));
+                            continue;
+                        }
+                        Err(_) => {
+                            error!("bad prebinned partitioning {:?}", self.range);
+                            Ready(None)
+                        }
+                    }
                 } else {
                     Ready(None)
                 }
diff --git a/src/timebinnedjson.rs b/src/timebinnedjson.rs
index e27ed6f..4388792 100644
--- a/src/timebinnedjson.rs
+++ b/src/timebinnedjson.rs
@@ -264,7 +264,6 @@ async fn timebinned_stream(
     cache_read_provider: Arc<dyn CacheReadProvider>,
     events_read_provider: Arc<dyn EventsReadProvider>,
 ) -> Result<Pin<Box<dyn Stream<Item = Sitemty<Box<dyn CollectableDyn>>> + Send>>, Error> {
-    use netpod::query::CacheUsage;
     let do_time_weight = true;
     let bin_len_layers = if let Some(subgrids) = query.subgrids() {
         subgrids