diff --git a/src/NT8.Core/MarketData/DataQualityValidator.cs b/src/NT8.Core/MarketData/DataQualityValidator.cs
new file mode 100644
index 0000000..6e9f446
--- /dev/null
+++ b/src/NT8.Core/MarketData/DataQualityValidator.cs
@@ -0,0 +1,275 @@
+using System;
+using System.Collections.Generic;
+using NT8.Core.Common.Models;
+
+namespace NT8.Core.MarketData
+{
+    /// <summary>
+    /// Validates market data quality and detects anomalies
+    /// </summary>
+    public class DataQualityValidator
+    {
+        /// <summary>
+        /// Configuration for data quality validation
+        /// </summary>
+        public class DataQualityConfig
+        {
+            /// <summary>
+            /// Maximum allowed price change percentage between consecutive bars
+            /// </summary>
+            public double MaxPriceChangePercent { get; set; }
+
+            /// <summary>
+            /// Minimum allowed volume for a bar to be considered valid
+            /// </summary>
+            public long MinVolume { get; set; }
+
+            /// <summary>
+            /// Maximum allowed volume spike multiplier compared to average
+            /// </summary>
+            public double MaxVolumeSpikeMultiplier { get; set; }
+
+            /// <summary>
+            /// Constructor for DataQualityConfig
+            /// </summary>
+            public DataQualityConfig()
+            {
+                MaxPriceChangePercent = 10.0; // 10% default
+                MinVolume = 1; // Minimum 1 volume
+                MaxVolumeSpikeMultiplier = 100.0; // 100x volume spike threshold
+            }
+        }
+
+        private readonly DataQualityConfig _config;
+        private readonly Dictionary<string, List<double>> _priceHistory;
+        private readonly Dictionary<string, List<long>> _volumeHistory;
+
+        /// <summary>
+        /// Constructor for DataQualityValidator
+        /// </summary>
+        public DataQualityValidator(DataQualityConfig config = null)
+        {
+            _config = config ?? new DataQualityConfig();
+            _priceHistory = new Dictionary<string, List<double>>();
+            _volumeHistory = new Dictionary<string, List<long>>();
+        }
+
+        /// <summary>
+        /// Validate bar data quality and detect anomalies
+        /// </summary>
+        public DataQualityResult ValidateBar(BarData currentBar, BarData previousBar = null)
+        {
+            if (currentBar == null)
+                throw new ArgumentNullException("currentBar");
+
+            var result = new DataQualityResult();
+
+            // Basic validation
+            if (!BasicBarValidation(currentBar))
+            {
+                result.IsValid = false;
+                result.Reasons.Add("Basic validation failed");
+                return result;
+            }
+
+            // Previous bar validation
+            if (previousBar != null)
+            {
+                // Price change validation
+                var priceChangePercent = CalculatePriceChangePercent(previousBar.Close, currentBar.Open);
+                if (Math.Abs(priceChangePercent) > _config.MaxPriceChangePercent)
+                {
+                    result.IsValid = false;
+                    result.Reasons.Add(string.Format("Price change {0:F2}% exceeds threshold of {1:F2}%",
+                        priceChangePercent, _config.MaxPriceChangePercent));
+                }
+
+                // Volume validation
+                if (currentBar.Volume < _config.MinVolume)
+                {
+                    result.IsValid = false;
+                    result.Reasons.Add(string.Format("Volume {0} below minimum threshold of {1}",
+                        currentBar.Volume, _config.MinVolume));
+                }
+
+                // Volume spike detection
+                var avgVolume = CalculateAverageVolume(previousBar.Symbol);
+                if (avgVolume > 0 && currentBar.Volume > avgVolume * _config.MaxVolumeSpikeMultiplier)
+                {
+                    result.IsValid = false;
+                    result.Reasons.Add(string.Format("Volume spike detected: {0} vs average {1:F0}",
+                        currentBar.Volume, avgVolume));
+                }
+            }
+
+            // Update history
+            UpdateHistory(currentBar);
+
+            result.IsValid = result.Reasons.Count == 0;
+            return result;
+        }
+
+        /// <summary>
+        /// Validate tick data quality and detect anomalies
+        /// </summary>
+        public DataQualityResult ValidateTick(TickData currentTick, TickData previousTick = null)
+        {
+            if (currentTick == null)
+                throw new ArgumentNullException("currentTick");
+
+            var result = new DataQualityResult();
+
+            // Basic validation
+            if (!BasicTickValidation(currentTick))
+            {
+                result.IsValid = false;
+                result.Reasons.Add("Basic validation failed");
+                return result;
+            }
+
+            // Previous tick validation
+            if (previousTick != null)
+            {
+                // Price change validation
+                var priceChangePercent = CalculatePriceChangePercent(previousTick.Price, currentTick.Price);
+                if (Math.Abs(priceChangePercent) > _config.MaxPriceChangePercent)
+                {
+                    result.IsValid = false;
+                    result.Reasons.Add(string.Format("Price change {0:F2}% exceeds threshold of {1:F2}%",
+                        priceChangePercent, _config.MaxPriceChangePercent));
+                }
+            }
+
+            result.IsValid = result.Reasons.Count == 0;
+            return result;
+        }
+
+        /// <summary>
+        /// Basic bar validation
+        /// </summary>
+        private bool BasicBarValidation(BarData bar)
+        {
+            // Check for reasonable price values
+            if (bar.Open <= 0 || bar.High <= 0 || bar.Low <= 0 || bar.Close <= 0)
+                return false;
+
+            // Check for valid high/low relationships
+            if (bar.High < bar.Low)
+                return false;
+
+            // Check if close price is within high/low range
+            if (bar.Close < bar.Low || bar.Close > bar.High)
+                return false;
+
+            // Check for reasonable volume
+            if (bar.Volume < 0)
+                return false;
+
+            return true;
+        }
+
+        /// <summary>
+        /// Basic tick validation
+        /// </summary>
+        private bool BasicTickValidation(TickData tick)
+        {
+            // Check for reasonable price values
+            if (tick.Price <= 0)
+                return false;
+
+            // Check for reasonable size
+            if (tick.Size < 0)
+                return false;
+
+            return true;
+        }
+
+        /// <summary>
+        /// Calculate price change percentage
+        /// </summary>
+        private double CalculatePriceChangePercent(double previousPrice, double currentPrice)
+        {
+            if (previousPrice == 0)
+                return 0;
+
+            return ((currentPrice - previousPrice) / previousPrice) * 100;
+        }
+
+        /// <summary>
+        /// Calculate average volume for a symbol
+        /// </summary>
+        private double CalculateAverageVolume(string symbol)
+        {
+            List<long> volumes;
+            if (!_volumeHistory.TryGetValue(symbol, out volumes) || volumes.Count == 0)
+                return 0;
+
+            long sum = 0;
+            foreach (var volume in volumes)
+            {
+                sum += volume;
+            }
+
+            return (double)sum / volumes.Count;
+        }
+
+        /// <summary>
+        /// Update price and volume history
+        /// </summary>
+        private void UpdateHistory(BarData bar)
+        {
+            // Update price history
+            List<double> prices;
+            if (!_priceHistory.TryGetValue(bar.Symbol, out prices))
+            {
+                prices = new List<double>();
+                _priceHistory[bar.Symbol] = prices;
+            }
+
+            prices.Add(bar.Close);
+            if (prices.Count > 100) // Keep only last 100 prices
+            {
+                prices.RemoveAt(0);
+            }
+
+            // Update volume history
+            List<long> volumes;
+            if (!_volumeHistory.TryGetValue(bar.Symbol, out volumes))
+            {
+                volumes = new List<long>();
+                _volumeHistory[bar.Symbol] = volumes;
+            }
+
+            volumes.Add(bar.Volume);
+            if (volumes.Count > 100) // Keep only last 100 volumes
+            {
+                volumes.RemoveAt(0);
+            }
+        }
+    }
+
+    /// <summary>
+    /// Result of data quality validation
+    /// </summary>
+    public class DataQualityResult
+    {
+        /// <summary>
+        /// Whether the data is valid
+        /// </summary>
+        public bool IsValid { get; set; }
+
+        /// <summary>
+        /// Reasons for validation failure
+        /// </summary>
+        public List<string> Reasons { get; set; }
+
+        /// <summary>
+        /// Constructor for DataQualityResult
+        /// </summary>
+        public DataQualityResult()
+        {
+            IsValid = true;
+            Reasons = new List<string>();
+        }
+    }
+}
diff --git a/src/NT8.Core/MarketData/HistoricalDataManager.cs b/src/NT8.Core/MarketData/HistoricalDataManager.cs
new file mode 100644
index 0000000..03d7402
--- /dev/null
+++ b/src/NT8.Core/MarketData/HistoricalDataManager.cs
@@ -0,0 +1,262 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.IO.Compression;
+using System.Text;
+using System.Threading.Tasks;
+using NT8.Core.Common.Models;
+
+namespace NT8.Core.MarketData
+{
+    /// <summary>
+    /// Manages historical market data storage, retrieval, and archiving
+    /// </summary>
+    public class HistoricalDataManager
+    {
+        private readonly string _dataDirectory;
+        private readonly bool _enableCompression;
+
+        /// <summary>
+        /// Constructor for HistoricalDataManager
+        /// </summary>
+        public HistoricalDataManager(string dataDirectory = null, bool enableCompression = true)
+        {
+            _dataDirectory = dataDirectory ?? Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ApplicationData), "NT8", "MarketData");
+            _enableCompression = enableCompression;
+
+            // Ensure data directory exists
+            if (!Directory.Exists(_dataDirectory))
+            {
+                Directory.CreateDirectory(_dataDirectory);
+            }
+        }
+
+        /// <summary>
+        /// Save historical bars to storage
+        /// </summary>
+        public async Task SaveHistoricalBars(string symbol, TimeSpan barSize, List<BarData> bars)
+        {
+            if (string.IsNullOrEmpty(symbol))
+                throw new ArgumentException("Symbol cannot be null or empty", "symbol");
+
+            if (bars == null)
+                throw new ArgumentNullException("bars");
+
+            var fileName = GenerateFileName(symbol, barSize, DateTime.UtcNow);
+            var filePath = Path.Combine(_dataDirectory, fileName);
+
+            // Convert bars to CSV format
+            var csv = ConvertBarsToCsv(bars);
+
+            if (_enableCompression)
+            {
+                await SaveCompressedFile(filePath + ".gz", csv);
+            }
+            else
+            {
+                await SaveTextFile(filePath + ".csv", csv);
+            }
+        }
+
+        /// <summary>
+        /// Load historical bars from storage
+        /// </summary>
+        public async Task<List<BarData>> LoadHistoricalBars(string symbol, TimeSpan barSize, DateTime date)
+        {
+            if (string.IsNullOrEmpty(symbol))
+                throw new ArgumentException("Symbol cannot be null or empty", "symbol");
+
+            var fileName = GenerateFileName(symbol, barSize, date);
+            var filePath = Path.Combine(_dataDirectory, fileName);
+
+            string csv;
+            if (_enableCompression)
+            {
+                filePath += ".gz";
+                if (!File.Exists(filePath))
+                    return new List<BarData>();
+
+                csv = await LoadCompressedFile(filePath);
+            }
+            else
+            {
+                filePath += ".csv";
+                if (!File.Exists(filePath))
+                    return new List<BarData>();
+
+                csv = await LoadTextFile(filePath);
+            }
+
+            // Convert CSV back to BarData
+            return ConvertCsvToBars(csv);
+        }
+
+        /// <summary>
+        /// Archive old data files
+        /// </summary>
+        public async Task ArchiveOldData(DateTime olderThan)
+        {
+            var archiveDirectory = Path.Combine(_dataDirectory, "Archive");
+            if (!Directory.Exists(archiveDirectory))
+            {
+                Directory.CreateDirectory(archiveDirectory);
+            }
+
+            var files = Directory.GetFiles(_dataDirectory, "*.csv*");
+            foreach (var file in files)
+            {
+                var fileName = Path.GetFileName(file);
+                var fileDate = ExtractDateFromFileName(fileName);
+
+                if (fileDate < olderThan)
+                {
+                    var archivePath = Path.Combine(archiveDirectory, fileName);
+                    await Task.Run(() => File.Move(file, archivePath));
+                }
+            }
+        }
+
+        /// <summary>
+        /// Generate file name for data storage
+        /// </summary>
+        private string GenerateFileName(string symbol, TimeSpan barSize, DateTime date)
+        {
+            return string.Format("{0}_{1}_{2:yyyyMMdd}", symbol, (int)barSize.TotalMinutes, date);
+        }
+
+        /// <summary>
+        /// Extract date from file name
+        /// </summary>
+        private DateTime ExtractDateFromFileName(string fileName)
+        {
+            // Extract date portion from file name
+            var parts = fileName.Split('_');
+            if (parts.Length >= 3)
+            {
+                var datePart = parts[2].Split('.')[0]; // Remove extension
+                DateTime date;
+                if (DateTime.TryParseExact(datePart, "yyyyMMdd", null, System.Globalization.DateTimeStyles.None, out date))
+                {
+                    return date;
+                }
+            }
+
+            return DateTime.MinValue;
+        }
+
+        /// <summary>
+        /// Convert bars to CSV format
+        /// </summary>
+        private string ConvertBarsToCsv(List<BarData> bars)
+        {
+            var sb = new StringBuilder();
+
+            // Header
+            sb.AppendLine("Symbol,Time,Open,High,Low,Close,Volume,BarSizeTicks");
+
+            // Data rows
+            foreach (var bar in bars)
+            {
+                sb.AppendFormat("{0},{1:yyyy-MM-dd HH:mm:ss},{2},{3},{4},{5},{6},{7}",
+                    bar.Symbol,
+                    bar.Time,
+                    bar.Open,
+                    bar.High,
+                    bar.Low,
+                    bar.Close,
+                    bar.Volume,
+                    bar.BarSize.Ticks);
+                sb.AppendLine();
+            }
+
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Convert CSV to bars
+        /// </summary>
+        private List<BarData> ConvertCsvToBars(string csv)
+        {
+            var bars = new List<BarData>();
+            var lines = csv.Split(new[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
+
+            // Skip header line
+            for (int i = 1; i < lines.Length; i++)
+            {
+                var fields = lines[i].Split(',');
+                if (fields.Length >= 8)
+                {
+                    try
+                    {
+                        var bar = new BarData(
+                            fields[0], // Symbol
+                            DateTime.Parse(fields[1]), // Time
+                            double.Parse(fields[2]), // Open
+                            double.Parse(fields[3]), // High
+                            double.Parse(fields[4]), // Low
+                            double.Parse(fields[5]), // Close
+                            long.Parse(fields[6]), // Volume
+                            TimeSpan.FromTicks(long.Parse(fields[7])) // BarSize
+                        );
+
+                        bars.Add(bar);
+                    }
+                    catch
+                    {
+                        // Skip invalid rows
+                    }
+                }
+            }
+
+            return bars;
+        }
+
+        /// <summary>
+        /// Save compressed file
+        /// </summary>
+        private async Task SaveCompressedFile(string filePath, string content)
+        {
+            using (var fileStream = new FileStream(filePath, FileMode.Create))
+            using (var gzipStream = new GZipStream(fileStream, CompressionMode.Compress))
+            using (var writer = new StreamWriter(gzipStream))
+            {
+                await writer.WriteAsync(content);
+            }
+        }
+
+        /// <summary>
+        /// Load compressed file
+        /// </summary>
+        private async Task<string> LoadCompressedFile(string filePath)
+        {
+            using (var fileStream = new FileStream(filePath, FileMode.Open))
+            using (var gzipStream = new GZipStream(fileStream, CompressionMode.Decompress))
+            using (var reader = new StreamReader(gzipStream))
+            {
+                return await reader.ReadToEndAsync();
+            }
+        }
+
+        /// <summary>
+        /// Save text file
+        /// </summary>
+        private async Task SaveTextFile(string filePath, string content)
+        {
+            using (var writer = new StreamWriter(filePath))
+            {
+                await writer.WriteAsync(content);
+            }
+        }
+
+        /// <summary>
+        /// Load text file
+        /// </summary>
+        private async Task<string> LoadTextFile(string filePath)
+        {
+            using (var reader = new StreamReader(filePath))
+            {
+                return await reader.ReadToEndAsync();
+            }
+        }
+    }
+}
diff --git a/src/NT8.Core/MarketData/MarketDataProvider.cs b/src/NT8.Core/MarketData/MarketDataProvider.cs
new file mode 100644
index 0000000..d2ac6c9
--- /dev/null
+++ b/src/NT8.Core/MarketData/MarketDataProvider.cs
@@ -0,0 +1,314 @@
+using System;
+using System.Collections.Concurrent;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using NT8.Core.Common.Models;
+
+namespace NT8.Core.MarketData
+{
+    /// <summary>
+    /// Base implementation of market data provider with caching and validation
+    /// </summary>
+    public class MarketDataProvider : IMarketDataProvider
+    {
+        // Data storage
+        private readonly ConcurrentDictionary<string, List<BarData>> _barCache;
+        private readonly ConcurrentDictionary<string, List<TickData>> _tickCache;
+        private readonly ConcurrentDictionary<string, double> _currentPrices;
+
+        // Subscriptions
+        private readonly ConcurrentDictionary<string, List<Action<BarData>>> _barSubscriptions;
+        private readonly ConcurrentDictionary<string, List<Action<TickData>>> _tickSubscriptions;
+
+        // Configuration
+        private readonly int _maxCacheSize;
+        private readonly TimeSpan _dataFreshnessTimeout;
+
+        /// <summary>
+        /// Constructor for MarketDataProvider
+        /// </summary>
+        public MarketDataProvider(int maxCacheSize = 10000, TimeSpan? dataFreshnessTimeout = null)
+        {
+            _barCache = new ConcurrentDictionary<string, List<BarData>>();
+            _tickCache = new ConcurrentDictionary<string, List<TickData>>();
+            _currentPrices = new ConcurrentDictionary<string, double>();
+            _barSubscriptions = new ConcurrentDictionary<string, List<Action<BarData>>>();
+            _tickSubscriptions = new ConcurrentDictionary<string, List<Action<TickData>>>();
+
+            _maxCacheSize = maxCacheSize;
+            _dataFreshnessTimeout = dataFreshnessTimeout ?? TimeSpan.FromMinutes(5);
+        }
+
+        /// <summary>
+        /// Subscribe to bar data
+        /// </summary>
+        public void SubscribeBars(string symbol, TimeSpan barSize, Action<BarData> onBar)
+        {
+            if (string.IsNullOrEmpty(symbol))
+                throw new ArgumentException("Symbol cannot be null or empty", "symbol");
+
+            if (onBar == null)
+                throw new ArgumentNullException("onBar");
+
+            string key = string.Format("{0}_{1}", symbol, barSize);
+            _barSubscriptions.AddOrUpdate(
+                key,
+                new List<Action<BarData>> { onBar },
+                (k, list) => { list.Add(onBar); return list; }
+            );
+        }
+
+        /// <summary>
+        /// Subscribe to tick data
+        /// </summary>
+        public void SubscribeTicks(string symbol, Action<TickData> onTick)
+        {
+            if (string.IsNullOrEmpty(symbol))
+                throw new ArgumentException("Symbol cannot be null or empty", "symbol");
+
+            if (onTick == null)
+                throw new ArgumentNullException("onTick");
+
+            _tickSubscriptions.AddOrUpdate(
+                symbol,
+                new List<Action<TickData>> { onTick },
+                (k, list) => { list.Add(onTick); return list; }
+            );
+        }
+
+        /// <summary>
+        /// Get historical bars
+        /// </summary>
+        public async Task<List<BarData>> GetHistoricalBars(string symbol, TimeSpan barSize, int count)
+        {
+            if (string.IsNullOrEmpty(symbol))
+                throw new ArgumentException("Symbol cannot be null or empty", "symbol");
+
+            if (count <= 0)
+                throw new ArgumentException("Count must be greater than zero", "count");
+
+            string key = string.Format("{0}_{1}", symbol, barSize);
+
+            List<BarData> bars;
+            if (_barCache.TryGetValue(key, out bars))
+            {
+                // Return the most recent bars, up to the requested count
+                var result = bars
+                    .OrderByDescending(b => b.Time)
+                    .Take(count)
+                    .ToList();
+
+                return await Task.FromResult(result);
+            }
+
+            // Return empty list if no data is available
+            return await Task.FromResult(new List<BarData>());
+        }
+
+        /// <summary>
+        /// Get current market price
+        /// </summary>
+        public double? GetCurrentPrice(string symbol)
+        {
+            if (string.IsNullOrEmpty(symbol))
+                throw new ArgumentException("Symbol cannot be null or empty", "symbol");
+
+            double price;
+            if (_currentPrices.TryGetValue(symbol, out price))
+            {
+                return price;
+            }
+            return null;
+        }
+
+        /// <summary>
+        /// Add bar data to the provider
+        /// </summary>
+        public void AddBarData(BarData bar)
+        {
+            if (bar == null)
+                throw new ArgumentNullException("bar");
+
+            string key = string.Format("{0}_{1}", bar.Symbol, bar.BarSize);
+
+            // Add to cache
+            _barCache.AddOrUpdate(
+                key,
+                new List<BarData> { bar },
+                (k, list) =>
+                {
+                    list.Add(bar);
+                    // Trim cache if it exceeds maximum size
+                    if (list.Count > _maxCacheSize)
+                    {
+                        list.RemoveRange(0, list.Count - _maxCacheSize);
+                    }
+                    return list;
+                }
+            );
+
+            // Update current price
+            _currentPrices[bar.Symbol] = bar.Close;
+
+            // Notify subscribers
+            List<Action<BarData>> subscribers;
+            if (_barSubscriptions.TryGetValue(key, out subscribers))
+            {
+                foreach (var subscriber in subscribers)
+                {
+                    try
+                    {
+                        subscriber(bar);
+                    }
+                    catch
+                    {
+                        // Ignore exceptions in subscriber callbacks
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Add tick data to the provider
+        /// </summary>
+        public void AddTickData(TickData tick)
+        {
+            if (tick == null)
+                throw new ArgumentNullException("tick");
+
+            // Add to cache
+            _tickCache.AddOrUpdate(
+                tick.Symbol,
+                new List<TickData> { tick },
+                (k, list) =>
+                {
+                    list.Add(tick);
+                    // Trim cache if it exceeds maximum size
+                    if (list.Count > _maxCacheSize)
+                    {
+                        list.RemoveRange(0, list.Count - _maxCacheSize);
+                    }
+                    return list;
+                }
+            );
+
+            // Update current price
+            _currentPrices[tick.Symbol] = tick.Price;
+
+            // Notify subscribers
+            List<Action<TickData>> subscribers;
+            if (_tickSubscriptions.TryGetValue(tick.Symbol, out subscribers))
+            {
+                foreach (var subscriber in subscribers)
+                {
+                    try
+                    {
+                        subscriber(tick);
+                    }
+                    catch
+                    {
+                        // Ignore exceptions in subscriber callbacks
+                    }
+                }
+            }
+        }
+
+        /// <summary>
+        /// Validate market data quality
+        /// </summary>
+        public bool ValidateDataQuality(BarData bar)
+        {
+            if (bar == null)
+                return false;
+
+            // Check for reasonable price values
+            if (bar.Open <= 0 || bar.High <= 0 || bar.Low <= 0 || bar.Close <= 0)
+                return false;
+
+            // Check for valid high/low relationships
+            if (bar.High < bar.Low)
+                return false;
+
+            // Check if close price is within high/low range
+            if (bar.Close < bar.Low || bar.Close > bar.High)
+                return false;
+
+            // Check for reasonable volume
+            if (bar.Volume < 0)
+                return false;
+
+            return true;
+        }
+
+        /// <summary>
+        /// Validate market data quality
+        /// </summary>
+        public bool ValidateDataQuality(TickData tick)
+        {
+            if (tick == null)
+                return false;
+
+            // Check for reasonable price values
+            if (tick.Price <= 0)
+                return false;
+
+            // Check for reasonable size
+            if (tick.Size < 0)
+                return false;
+
+            return true;
+        }
+
+        /// <summary>
+        /// Get data freshness information
+        /// </summary>
+        public DateTime? GetLastUpdateTime(string symbol)
+        {
+            if (string.IsNullOrEmpty(symbol))
+                return null;
+
+            // Check bars for this symbol
+            var barKeys = _barCache.Keys.Where(k => k.StartsWith(string.Format("{0}_", symbol))).ToList();
+            DateTime? latestBarTime = null;
+
+            foreach (var key in barKeys)
+            {
+                List<BarData> bars;
+                if (_barCache.TryGetValue(key, out bars) && bars.Count > 0)
+                {
+                    var lastBarTime = bars.Max(b => b.Time);
+                    if (latestBarTime == null || lastBarTime > latestBarTime)
+                    {
+                        latestBarTime = lastBarTime;
+                    }
+                }
+            }
+
+            // Check ticks for this symbol
+            List<TickData> ticks;
+            if (_tickCache.TryGetValue(symbol, out ticks) && ticks.Count > 0)
+            {
+                var lastTickTime = ticks.Max(t => t.Time);
+                if (latestBarTime == null || lastTickTime > latestBarTime)
+                {
+                    latestBarTime = lastTickTime;
+                }
+            }
+
+            return latestBarTime;
+        }
+
+        /// <summary>
+        /// Check if data is fresh
+        /// </summary>
+        public bool IsDataFresh(string symbol)
+        {
+            DateTime? lastUpdate = GetLastUpdateTime(symbol);
+            if (lastUpdate == null)
+                return false;
+
+            return DateTime.UtcNow - lastUpdate.Value < _dataFreshnessTimeout;
+        }
+    }
+}