diff --git a/CHANGELOG.md b/CHANGELOG.md
index ecaabad3f..3c16bb5f8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,9 @@ The `Unreleased` section name is replaced by the expected version of next releas
 - `CosmosStore`: Require `Microsoft.Azure.Cosmos` v `3.0.25` [#310](https://github.com/jet/equinox/pull/310)
 - `SqlStreamStore`.*: Target `SqlStreamStore` v `1.2.0` (`Postgres` remains at `1.2.0-beta.8` as that's the last released version) [#227](https://github.com/jet/equinox/pull/227) :pray: [@rajivhost](https://github.com/rajivhost)
 - Update all non-Client dependencies except `FSharp.Core`, `FSharp.Control.AsyncSeq` [#310](https://github.com/jet/equinox/pull/310)
+- `CosmosStore`: Switch to natively using `JsonElement` event bodies [#305](https://github.com/jet/equinox/pull/305) :pray: [@ylibrach](https://github.com/ylibrach)
+- `CosmosStore`: Switch to natively using `System.Text.Json` for serialization of all `Microsoft.Azure.Cosmos` round-trips [#305](https://github.com/jet/equinox/pull/305) :pray: [@ylibrach](https://github.com/ylibrach)
+- `CosmosStore`: Only log `bytes` when log level is `Debug` [#305](https://github.com/jet/equinox/pull/305)
 
 ### Removed
  
diff --git a/src/Equinox.CosmosStore/CosmosStore.fs b/src/Equinox.CosmosStore/CosmosStore.fs
index 8163fe7ea..a6623635a 100644
--- a/src/Equinox.CosmosStore/CosmosStore.fs
+++ b/src/Equinox.CosmosStore/CosmosStore.fs
@@ -230,10 +230,10 @@ module Log =
     let internal event (value : Metric) (log : ILogger) =
         let enrich (e : Serilog.Events.LogEvent) =
             e.AddPropertyIfAbsent(Serilog.Events.LogEventProperty(PropertyTag, Serilog.Events.ScalarValue(value)))
-        log.ForContext({ new Serilog.Core.ILogEventEnricher with member _.Enrich(evt, _) = enrich evt })
+        log.ForContext({ new Serilog.Core.ILogEventEnricher with member _.Enrich(evt,_) = enrich evt })
     let internal (|BlobLen|) (x : EventBody) = if x.ValueKind = JsonValueKind.Null then 0 else x.GetRawText().Length
-    let internal (|EventLen|) (x : #IEventData<_>) = let BlobLen bytes, BlobLen metaBytes = x.Data, x.Meta in bytes + metaBytes + 80
-    let internal (|BatchLen|) = Seq.sumBy (|EventLen|)
+    let internal eventLen (x: #IEventData<_>) = let BlobLen bytes, BlobLen metaBytes = x.Data, x.Meta in bytes + metaBytes + 80
+    let internal batchLen = Seq.sumBy eventLen
     let internal (|SerilogScalar|_|) : Serilog.Events.LogEventPropertyValue -> obj option = function
         | :? Serilog.Events.ScalarValue as x -> Some x.Value
         | _ -> None
@@ -479,12 +479,12 @@ module internal Sync =
     let private logged (container, stream) (maxEventsInTip, maxStringifyLen) (exp : SyncExp, req : Tip) (log : ILogger)
         : Async<Result> = async {
         let! t, (ru, result) = run (container, stream) (maxEventsInTip, maxStringifyLen) (exp, req) |> Stopwatch.Time
-        let Log.BatchLen bytes, count = Enum.Events req, req.e.Length
+        let verbose = log.IsEnabled Serilog.Events.LogEventLevel.Debug
+        let count, bytes = req.e.Length, if verbose then Enum.Events req |> Log.batchLen else 0
         let log =
             let inline mkMetric ru : Log.Measurement =
                 { database = container.Database.Id; container = container.Id; stream = stream; interval = t; bytes = bytes; count = count; ru = ru }
             let inline propConflict log = log |> Log.prop "conflict" true |> Log.prop "eventTypes" (Seq.truncate 5 (seq { for x in req.e -> x.c }))
-            let verbose = log.IsEnabled Events.LogEventLevel.Debug
             if verbose then log |> Log.propEvents (Enum.Events req) |> Log.propDataUnfolds req.u else log
             |> match exp with
                 | SyncExp.Etag et ->     Log.prop "expectedEtag" et
@@ -613,7 +613,7 @@ module internal Tip =
             (log 0 0 Log.Metric.TipNotFound).Information("EqxCosmos {action:l} {stream} {res} {ms}ms rc={ru}", "Tip", stream, 404, (let e = t.Elapsed in e.TotalMilliseconds), ru)
         | ReadResult.Found tip ->
             let log =
-                let Log.BatchLen bytes, count = Enum.Unfolds tip.u, tip.u.Length
+                let count, bytes = tip.u.Length, if verbose then Enum.Unfolds tip.u |> Log.batchLen else 0
                 log bytes count Log.Metric.Tip
             let log = if verbose then log |> Log.propDataUnfolds tip.u else log
             let log = match maybePos with Some p -> log |> Log.propStartPos p |> Log.propStartEtag p | None -> log
@@ -642,7 +642,7 @@ module internal Query =
             if query.HasMoreResults then
                 yield! loop (i + 1) }
         // earlier versions, such as 3.9.0, do not implement IDisposable; see linked issue for detail on when SDK team added it
-        use __ = query // see https://github.com/jet/equinox/issues/225 - in the Cosmos V4 SDK, all this is managed IAsyncEnumerable
+        use _ = query // see https://github.com/jet/equinox/issues/225 - in the Cosmos V4 SDK, all this is managed IAsyncEnumerable
         loop 0
     let private mkQuery (log : ILogger) (container : Container, stream : string) includeTip maxItems (direction : Direction, minIndex, maxIndex) : FeedIterator<Batch> =
         let order = if direction = Direction.Forward then "ASC" else "DESC"
@@ -676,10 +676,10 @@ module internal Query =
             Enum.Events(b, ?minIndex = minIndex, ?maxIndex = maxIndex)
             |> if direction = Direction.Backward then System.Linq.Enumerable.Reverse else id
         let events = batches |> Seq.collect unwrapBatch |> Array.ofSeq
-        let Log.BatchLen bytes, count = events, events.Length
+        let verbose = log.IsEnabled Events.LogEventLevel.Debug
+        let count, bytes = events.Length, if verbose then events |> Log.batchLen else 0
         let reqMetric : Log.Measurement = { database = container.Database.Id; container = container.Id; stream = streamName; interval = t; bytes = bytes; count = count; ru = ru }
         let log = let evt = Log.Metric.QueryResponse (direction, reqMetric) in log |> Log.event evt
-        let verbose = log.IsEnabled Events.LogEventLevel.Debug
         let log = if verbose then log |> Log.propEvents events else log
         let index = if count = 0 then Nullable () else Nullable <| Seq.min (seq { for x in batches -> x.i })
         (log|> Log.prop "bytes" bytes
@@ -691,7 +691,8 @@ module internal Query =
         events, maybePosition, ru
 
     let private logQuery direction queryMaxItems (container : Container, streamName) interval (responsesCount, events : ITimelineEvent<EventBody>[]) n (ru : float) (log : ILogger) =
-        let Log.BatchLen bytes, count = events, events.Length
+        let verbose = log.IsEnabled Events.LogEventLevel.Debug
+        let count, bytes = events.Length, if verbose then events |> Log.batchLen else 0
         let reqMetric : Log.Measurement = { database = container.Database.Id; container = container.Id; stream = streamName; interval = interval; bytes = bytes; count = count; ru = ru }
         let evt = Log.Metric.Query (direction, responsesCount, reqMetric)
         let action = match direction with Direction.Forward -> "QueryF" | Direction.Backward -> "QueryB"
@@ -703,7 +704,7 @@ module internal Query =
         let mutable used, dropped = 0, 0
         let mutable found = false
         for x in xs do
-            let (Log.EventLen bytes) = x
+            let bytes = Log.eventLen x
             if found then dropped <- dropped + bytes
             else used <- used + bytes
             if x.Index = stopIndex then found <- true