diff --git a/roboquant/src/main/kotlin/org/roboquant/loggers/LastEntryLogger.kt b/roboquant/src/main/kotlin/org/roboquant/loggers/LastEntryLogger.kt
index a7fe1529c..978b3bb81 100644
--- a/roboquant/src/main/kotlin/org/roboquant/loggers/LastEntryLogger.kt
+++ b/roboquant/src/main/kotlin/org/roboquant/loggers/LastEntryLogger.kt
@@ -20,7 +20,7 @@ import org.roboquant.common.Observation
 import org.roboquant.common.TimeSeries
 import org.roboquant.common.Timeframe
 import java.time.Instant
-import java.util.*
+import java.util.concurrent.ConcurrentHashMap
 
 /**
  * Stores the last value of a metric for a particular run in memory.
@@ -34,10 +34,9 @@ import java.util.*
 class LastEntryLogger(var showProgress: Boolean = false) : MetricsLogger {
 
     // The key is runName
-    private val history = Hashtable<String, MutableMap<String, Observation>>()
+    private val history = ConcurrentHashMap<String, MutableMap<String, Observation>>()
     private val progressBar = ProgressBar()
 
-    @Synchronized
     override fun log(results: Map<String, Double>, time: Instant, run: String) {
         if (showProgress) progressBar.update(time)
 
@@ -75,7 +74,6 @@ class LastEntryLogger(var showProgress: Boolean = false) : MetricsLogger {
     /**
      * Get results for the metric specified by its [name].
      */
-    @Synchronized
     override fun getMetric(name: String): Map<String, TimeSeries> {
         val result = mutableMapOf<String, TimeSeries>()
         for (run in history.keys) {
diff --git a/roboquant/src/main/kotlin/org/roboquant/loggers/MemoryLogger.kt b/roboquant/src/main/kotlin/org/roboquant/loggers/MemoryLogger.kt
index 363c5989f..925a000d9 100644
--- a/roboquant/src/main/kotlin/org/roboquant/loggers/MemoryLogger.kt
+++ b/roboquant/src/main/kotlin/org/roboquant/loggers/MemoryLogger.kt
@@ -19,6 +19,7 @@ package org.roboquant.loggers
 import org.roboquant.common.TimeSeries
 import org.roboquant.common.Timeframe
 import java.time.Instant
+import java.util.concurrent.ConcurrentHashMap
 
 /**
  * Store metric results in memory. Very convenient in a Jupyter notebook when you want to inspect or visualize
@@ -37,13 +38,14 @@ class MemoryLogger(var showProgress: Boolean = true) : MetricsLogger {
 
     internal class Entry(val time: Instant, val metrics: Map<String, Double>)
 
-    internal val history = mutableMapOf<String, MutableList<Entry>>()
+    // Use a ConcurrentHashMap if this logger is used in parallel back-testing
+    internal val history = ConcurrentHashMap<String, MutableList<Entry>>()
     private val progressBar = ProgressBar()
 
-    @Synchronized
     override fun log(results: Map<String, Double>, time: Instant, run: String) {
         if (showProgress) progressBar.update(time)
         if (results.isEmpty()) return
+
         val entries = history.getOrPut(run) { mutableListOf() }
         entries.add(Entry(time, results))
     }
@@ -71,7 +73,7 @@ class MemoryLogger(var showProgress: Boolean = true) : MetricsLogger {
      * Get all the recorded runs in this logger
      */
     val runs: Set<String>
-        get() = history.keys
+        get() = history.keys.toSortedSet()
 
     /**
      * Get the unique list of metric names that have been captured
@@ -88,7 +90,7 @@ class MemoryLogger(var showProgress: Boolean = true) : MetricsLogger {
             val ts = getMetric(name, run)
             if (ts.isNotEmpty()) result[run] = ts
         }
-        return result
+        return result.toSortedMap()
     }
 
     /**
diff --git a/roboquant/src/test/kotlin/org/roboquant/common/TimeframeTest.kt b/roboquant/src/test/kotlin/org/roboquant/common/TimeframeTest.kt
index 2b33c5024..db5ca11c4 100644
--- a/roboquant/src/test/kotlin/org/roboquant/common/TimeframeTest.kt
+++ b/roboquant/src/test/kotlin/org/roboquant/common/TimeframeTest.kt
@@ -73,6 +73,14 @@ internal class TimeframeTest {
         assertTrue(subFrames.all { it.start >= tf.start })
         assertTrue(subFrames.all { it.end <= tf.end })
         assertTrue(subFrames.all { it.end == it.start + 2.months })
+
+        tf.split(1.years).forEach { period ->
+            period.sample(1.months, 100).forEach {
+                assertTrue(period.contains(it.start))
+                assertTrue(period.contains(it.end))
+            }
+        }
+
     }
 
     @Test
diff --git a/roboquant/src/test/kotlin/org/roboquant/loggers/MemoryLoggerTest.kt b/roboquant/src/test/kotlin/org/roboquant/loggers/MemoryLoggerTest.kt
index 38e0acb80..36bdb958e 100644
--- a/roboquant/src/test/kotlin/org/roboquant/loggers/MemoryLoggerTest.kt
+++ b/roboquant/src/test/kotlin/org/roboquant/loggers/MemoryLoggerTest.kt
@@ -16,11 +16,10 @@
 
 package org.roboquant.loggers
 
+import kotlinx.coroutines.launch
 import org.junit.jupiter.api.assertThrows
 import org.roboquant.TestData
-import org.roboquant.common.Timeframe
-import org.roboquant.common.days
-import org.roboquant.common.plus
+import org.roboquant.common.*
 import org.roboquant.metrics.metricResultsOf
 import java.time.Instant
 import java.time.temporal.ChronoUnit
@@ -61,6 +60,35 @@ internal class MemoryLoggerTest {
         }
     }
 
+    @Test
+    fun concurrency() {
+        val logger = MemoryLogger(false)
+        val jobs = ParallelJobs()
+        Timeframe.fromYears(2000, 2002).split(1.months).forEach {
+            jobs.add {
+                launch {
+                    it.sample(1.days, 100).forEach { tf ->
+                        val run = "run-$tf"
+                        logger.start(run, tf)
+                        repeat(1000) {
+                            logger.log(mapOf("a" to 100.0 + it), tf.start + it.seconds, run)
+                        }
+                        logger.end(run)
+                    }
+                }
+            }
+
+        }
+        jobs.joinAllBlocking()
+        val data = logger.getMetric("a")
+        for (ts in data.values) {
+            assertEquals(1000, ts.size)
+            assertEquals(100.0, ts.values[0])
+        }
+
+    }
+
+
     @Test
     fun testMetricsEntry() {
         val logger = MemoryLogger(showProgress = false)