diff --git a/backend/config.py b/backend/config.py
index 2c4442a..183d1f1 100644
--- a/backend/config.py
+++ b/backend/config.py
@@ -250,9 +250,28 @@ class SinksConfig:
     fire_wood_cost_per_night: int = 1       # Wood consumed to stay warm at night
 
 
+@dataclass
+class PerformanceConfig:
+    """Configuration for performance optimization.
+
+    Controls logging and memory usage to keep simulation fast at high turn counts.
+    """
+    # Logging control
+    logging_enabled: bool = False           # Enable file logging (disable for speed)
+    detailed_logging: bool = False          # Enable verbose per-agent logging
+    log_flush_interval: int = 50            # Flush logs every N turns (not every turn)
+
+    # Memory management
+    max_turn_logs: int = 100                # Keep only last N turn logs in memory
+
+    # Statistics calculation frequency
+    stats_update_interval: int = 10         # Update expensive stats every N turns
+
+
 @dataclass
 class SimulationConfig:
     """Master configuration containing all sub-configs."""
+    performance: PerformanceConfig = field(default_factory=PerformanceConfig)
     agent_stats: AgentStatsConfig = field(default_factory=AgentStatsConfig)
     resources: ResourceConfig = field(default_factory=ResourceConfig)
     actions: ActionConfig = field(default_factory=ActionConfig)
@@ -270,6 +289,7 @@ class SimulationConfig:
     def to_dict(self) -> dict:
         """Convert to dictionary."""
         return {
+            "performance": asdict(self.performance),
             "ai": asdict(self.ai),
             "agent_stats": asdict(self.agent_stats),
             "resources": asdict(self.resources),
@@ -287,6 +307,7 @@ class SimulationConfig:
     def from_dict(cls, data: dict) -> "SimulationConfig":
         """Create from dictionary."""
         return cls(
+            performance=PerformanceConfig(**data.get("performance", {})),
             ai=AIConfig(**data.get("ai", {})),
             agent_stats=AgentStatsConfig(**data.get("agent_stats", {})),
             resources=ResourceConfig(**data.get("resources", {})),
@@ -387,3 +408,9 @@ def _reset_all_caches() -> None:
     except ImportError:
         pass
 
+    try:
+        from backend.core.ai import reset_ai_config_cache
+        reset_ai_config_cache()
+    except ImportError:
+        pass
+
diff --git a/backend/core/ai.py b/backend/core/ai.py
index e13e204..72aa712 100644
--- a/backend/core/ai.py
+++ b/backend/core/ai.py
@@ -101,18 +101,34 @@ def get_energy_cost(resource_type: ResourceType) -> int:
     return int(energy_cost / avg_output)
 
 
+# Cached config values to avoid repeated lookups
+_cached_ai_config = None
+_cached_economy_config = None
+
+
 def _get_ai_config():
-    """Get AI-relevant configuration values."""
-    from backend.config import get_config
-    config = get_config()
-    return config.agent_stats
+    """Get AI-relevant configuration values (cached)."""
+    global _cached_ai_config
+    if _cached_ai_config is None:
+        from backend.config import get_config
+        _cached_ai_config = get_config().agent_stats
+    return _cached_ai_config
 
 
 def _get_economy_config():
-    """Get economy/market configuration values."""
-    from backend.config import get_config
-    config = get_config()
-    return getattr(config, 'economy', None)
+    """Get economy/market configuration values (cached)."""
+    global _cached_economy_config
+    if _cached_economy_config is None:
+        from backend.config import get_config
+        _cached_economy_config = getattr(get_config(), 'economy', None)
+    return _cached_economy_config
+
+
+def reset_ai_config_cache():
+    """Reset the cached config values (call after config reload)."""
+    global _cached_ai_config, _cached_economy_config
+    _cached_ai_config = None
+    _cached_economy_config = None
 
 
 class AgentAI:
diff --git a/backend/core/engine.py b/backend/core/engine.py
index 24285c4..9642a8a 100644
--- a/backend/core/engine.py
+++ b/backend/core/engine.py
@@ -299,7 +299,12 @@ class GameEngine:
             self.is_running = False
             self.logger.close()
 
+        # Keep turn_logs bounded to prevent memory growth
+        max_logs = get_config().performance.max_turn_logs
         self.turn_logs.append(turn_log)
+        if len(self.turn_logs) > max_logs:
+            # Remove oldest logs, keep only recent ones
+            self.turn_logs = self.turn_logs[-max_logs:]
         return turn_log
 
     def _mark_dead_agents(self, current_turn: int) -> list[Agent]:
@@ -342,6 +347,8 @@ class GameEngine:
 
         for agent in to_remove:
             self.world.agents.remove(agent)
+            # Remove from index as well
+            self.world._agent_index.pop(agent.id, None)
             # Note: death was already recorded in _mark_dead_agents
 
         return to_remove
diff --git a/backend/core/logger.py b/backend/core/logger.py
index 30b1249..07dbd34 100644
--- a/backend/core/logger.py
+++ b/backend/core/logger.py
@@ -1,4 +1,7 @@
-"""Simulation logger for detailed step-by-step logging."""
+"""Simulation logger for detailed step-by-step logging.
+
+Performance-optimized: logging can be disabled or reduced via config.
+"""
 
 import json
 import logging
@@ -58,61 +61,77 @@ class TurnLogEntry:
 
 
 class SimulationLogger:
-    """Logger that dumps detailed simulation data to files."""
+    """Logger that dumps detailed simulation data to files.
+
+    Performance optimized:
+    - Logging can be disabled entirely via config
+    - File flushing is batched (not every turn)
+    - Agent lookups use O(1) dict instead of O(n) list search
+    - No in-memory accumulation of all entries
+    """
 
     def __init__(self, log_dir: str = "logs"):
         self.log_dir = Path(log_dir)
+
+        # Load performance config
+        from backend.config import get_config
+        perf_config = get_config().performance
+        self.logging_enabled = perf_config.logging_enabled
+        self.detailed_logging = perf_config.detailed_logging
+        self.flush_interval = perf_config.log_flush_interval
+
+        # File handles (only created if logging enabled)
+        self._json_file: Optional[TextIO] = None
+        self._summary_file: Optional[TextIO] = None
+
+        # Standard Python logging (minimal overhead even when enabled)
+        self.logger = logging.getLogger("simulation")
+        self.logger.setLevel(logging.WARNING)  # Only warnings by default
+
+        # Current turn tracking
+        self._current_entry: Optional[TurnLogEntry] = None
+        # O(1) lookup for agent entries by ID
+        self._agent_entry_map: dict[str, AgentLogEntry] = {}
+
+        # Turn counter for flush batching
+        self._turns_since_flush = 0
+
+    def start_session(self, config: dict) -> None:
+        """Start a new logging session."""
+        if not self.logging_enabled:
+            return
+
         self.log_dir.mkdir(exist_ok=True)
 
         # Create session-specific log file
         timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
-        self.session_file = self.log_dir / f"sim_{timestamp}.jsonl"
-        self.summary_file = self.log_dir / f"sim_{timestamp}_summary.txt"
+        session_file = self.log_dir / f"sim_{timestamp}.jsonl"
+        summary_file = self.log_dir / f"sim_{timestamp}_summary.txt"
 
-        # File handles
-        self._json_file: Optional[TextIO] = None
-        self._summary_file: Optional[TextIO] = None
-
-        # Also set up standard Python logging
-        self.logger = logging.getLogger("simulation")
-        self.logger.setLevel(logging.DEBUG)
-
-        # File handler for detailed logs
-        file_handler = logging.FileHandler(self.log_dir / f"sim_{timestamp}.log")
-        file_handler.setLevel(logging.DEBUG)
-        file_handler.setFormatter(logging.Formatter(
-            "%(asctime)s | %(levelname)s | %(message)s"
-        ))
-        self.logger.addHandler(file_handler)
-
-        # Console handler for important events
-        console_handler = logging.StreamHandler()
-        console_handler.setLevel(logging.INFO)
-        console_handler.setFormatter(logging.Formatter(
-            "%(asctime)s | %(message)s", datefmt="%H:%M:%S"
-        ))
-        self.logger.addHandler(console_handler)
-
-        self._entries: list[TurnLogEntry] = []
-        self._current_entry: Optional[TurnLogEntry] = None
-
-    def start_session(self, config: dict) -> None:
-        """Start a new logging session."""
-        self._json_file = open(self.session_file, "w")
-        self._summary_file = open(self.summary_file, "w")
+        self._json_file = open(session_file, "w")
+        self._summary_file = open(summary_file, "w")
 
         # Write config as first line
         self._json_file.write(json.dumps({"type": "config", "data": config}) + "\n")
-        self._json_file.flush()
 
         self._summary_file.write(f"Simulation Session Started: {datetime.now()}\n")
         self._summary_file.write("=" * 60 + "\n\n")
-        self._summary_file.flush()
 
-        self.logger.info(f"Logging session started: {self.session_file}")
+        if self.detailed_logging:
+            # Set up file handler for detailed logs
+            file_handler = logging.FileHandler(self.log_dir / f"sim_{timestamp}.log")
+            file_handler.setLevel(logging.DEBUG)
+            file_handler.setFormatter(logging.Formatter(
+                "%(asctime)s | %(levelname)s | %(message)s"
+            ))
+            self.logger.addHandler(file_handler)
+            self.logger.setLevel(logging.DEBUG)
 
     def start_turn(self, turn: int, day: int, step_in_day: int, time_of_day: str) -> None:
         """Start logging a new turn."""
+        if not self.logging_enabled:
+            return
+
         self._current_entry = TurnLogEntry(
             turn=turn,
             day=day,
@@ -120,7 +139,10 @@ class SimulationLogger:
             time_of_day=time_of_day,
             timestamp=datetime.now().isoformat(),
         )
-        self.logger.debug(f"Turn {turn} started (Day {day}, Step {step_in_day}, {time_of_day})")
+        self._agent_entry_map.clear()
+
+        if self.detailed_logging:
+            self.logger.debug(f"Turn {turn} started (Day {day}, Step {step_in_day}, {time_of_day})")
 
     def log_agent_before(
         self,
@@ -133,39 +155,41 @@ class SimulationLogger:
         money: int,
     ) -> None:
         """Log agent state before action."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
 
-        # Create placeholder entry
+        # Create entry and add to both list and map
         entry = AgentLogEntry(
             agent_id=agent_id,
             agent_name=agent_name,
             profession=profession,
-            position=position.copy(),
-            stats_before=stats.copy(),
+            position=position,
+            stats_before=stats,
             stats_after={},
             decision={},
             action_result={},
-            inventory_before=inventory.copy(),
+            inventory_before=inventory,
             inventory_after=[],
             money_before=money,
             money_after=money,
         )
         self._current_entry.agent_entries.append(entry)
+        self._agent_entry_map[agent_id] = entry
 
     def log_agent_decision(self, agent_id: str, decision: dict) -> None:
         """Log agent's AI decision."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
 
-        for entry in self._current_entry.agent_entries:
-            if entry.agent_id == agent_id:
-                entry.decision = decision.copy()
+        # O(1) lookup instead of O(n) search
+        entry = self._agent_entry_map.get(agent_id)
+        if entry:
+            entry.decision = decision
+            if self.detailed_logging:
                 self.logger.debug(
                     f"  {entry.agent_name}: decided to {decision.get('action', '?')} "
                     f"- {decision.get('reason', '')}"
                 )
-                break
 
     def log_agent_after(
         self,
@@ -177,102 +201,115 @@ class SimulationLogger:
         action_result: dict,
     ) -> None:
         """Log agent state after action."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
 
-        for entry in self._current_entry.agent_entries:
-            if entry.agent_id == agent_id:
-                entry.stats_after = stats.copy()
-                entry.inventory_after = inventory.copy()
-                entry.money_after = money
-                entry.position = position.copy()
-                entry.action_result = action_result.copy()
-                break
+        # O(1) lookup instead of O(n) search
+        entry = self._agent_entry_map.get(agent_id)
+        if entry:
+            entry.stats_after = stats
+            entry.inventory_after = inventory
+            entry.money_after = money
+            entry.position = position
+            entry.action_result = action_result
 
     def log_market_state(self, orders_before: list, orders_after: list) -> None:
         """Log market state."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
         self._current_entry.market_orders_before = orders_before
         self._current_entry.market_orders_after = orders_after
 
     def log_trade(self, trade: dict) -> None:
         """Log a trade transaction."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
         self._current_entry.trades.append(trade)
-        self.logger.debug(f"  Trade: {trade.get('message', 'Unknown trade')}")
+        if self.detailed_logging:
+            self.logger.debug(f"  Trade: {trade.get('message', 'Unknown trade')}")
 
     def log_death(self, agent_name: str, cause: str) -> None:
         """Log an agent death."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
         self._current_entry.deaths.append({"name": agent_name, "cause": cause})
+        # Always log deaths even without detailed logging
         self.logger.info(f"  DEATH: {agent_name} died from {cause}")
 
     def log_event(self, event_type: str, event_data: dict) -> None:
         """Log a general event (births, random events, etc.)."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
 
         if event_type == "birth":
             self.logger.info(
                 f"  BIRTH: {event_data.get('child_name', '?')} born to {event_data.get('parent_name', '?')}"
             )
-        elif event_type == "random_event":
+        elif event_type == "random_event" and self.detailed_logging:
             self.logger.info(
                 f"  EVENT: {event_data.get('type', '?')} affecting {event_data.get('affected', [])}"
             )
-        else:
+        elif self.detailed_logging:
             self.logger.debug(f"  Event [{event_type}]: {event_data}")
 
     def log_statistics(self, stats: dict) -> None:
         """Log end-of-turn statistics."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
-        self._current_entry.statistics = stats.copy()
+        self._current_entry.statistics = stats
 
     def end_turn(self) -> None:
         """Finish logging the current turn and write to file."""
-        if self._current_entry is None:
+        if not self.logging_enabled or self._current_entry is None:
             return
 
-        self._entries.append(self._current_entry)
-
-        # Write to JSON lines file
+        # Write to JSON lines file (without flush every time)
         if self._json_file:
             self._json_file.write(
                 json.dumps({"type": "turn", "data": self._current_entry.to_dict()}) + "\n"
             )
-            self._json_file.flush()
 
-        # Write summary
+        # Write summary (without flush every time)
         if self._summary_file:
             entry = self._current_entry
             self._summary_file.write(
                 f"Turn {entry.turn} | Day {entry.day} Step {entry.step_in_day} ({entry.time_of_day})\n"
             )
 
-            for agent in entry.agent_entries:
-                action = agent.decision.get("action", "?")
-                result = "✓" if agent.action_result.get("success", False) else "✗"
-                self._summary_file.write(
-                    f"  [{agent.agent_name}] {action} {result} | "
-                    f"E:{agent.stats_after.get('energy', '?')} "
-                    f"H:{agent.stats_after.get('hunger', '?')} "
-                    f"T:{agent.stats_after.get('thirst', '?')} "
-                    f"${agent.money_after}\n"
-                )
+            if self.detailed_logging:
+                for agent in entry.agent_entries:
+                    action = agent.decision.get("action", "?")
+                    result = "✓" if agent.action_result.get("success", False) else "✗"
+                    self._summary_file.write(
+                        f"  [{agent.agent_name}] {action} {result} | "
+                        f"E:{agent.stats_after.get('energy', '?')} "
+                        f"H:{agent.stats_after.get('hunger', '?')} "
+                        f"T:{agent.stats_after.get('thirst', '?')} "
+                        f"${agent.money_after}\n"
+                    )
 
             if entry.deaths:
                 for death in entry.deaths:
                     self._summary_file.write(f"  💀 {death['name']} died: {death['cause']}\n")
 
             self._summary_file.write("\n")
-            self._summary_file.flush()
 
-        self.logger.debug(f"Turn {self._current_entry.turn} completed")
+        # Batched flush - only flush every N turns
+        self._turns_since_flush += 1
+        if self._turns_since_flush >= self.flush_interval:
+            self._flush_files()
+            self._turns_since_flush = 0
+
+        # Clear current entry (don't accumulate in memory)
         self._current_entry = None
+        self._agent_entry_map.clear()
+
+    def _flush_files(self) -> None:
+        """Flush file buffers to disk."""
+        if self._json_file:
+            self._json_file.flush()
+        if self._summary_file:
+            self._summary_file.flush()
 
     def close(self) -> None:
         """Close log files."""
@@ -283,11 +320,13 @@ class SimulationLogger:
             self._summary_file.write(f"\nSession ended: {datetime.now()}\n")
             self._summary_file.close()
             self._summary_file = None
-        self.logger.info("Logging session closed")
 
     def get_entries(self) -> list[TurnLogEntry]:
-        """Get all logged entries."""
-        return self._entries.copy()
+        """Get all logged entries.
+
+        Note: Returns empty list when logging optimized (entries not kept in memory).
+        """
+        return []
 
 
 # Global logger instance
@@ -309,4 +348,3 @@ def reset_simulation_logger() -> SimulationLogger:
         _logger.close()
     _logger = SimulationLogger()
     return _logger
-
diff --git a/backend/core/market.py b/backend/core/market.py
index a447780..ba27c96 100644
--- a/backend/core/market.py
+++ b/backend/core/market.py
@@ -294,6 +294,9 @@ class OrderBook:
         # Record sale for price history (we need current_turn but don't have it here)
         # The turn will be passed via the _record_sale call from engine
         self.trade_history.append(result)
+        # Keep trade history bounded to prevent memory growth
+        if len(self.trade_history) > 1000:
+            self.trade_history = self.trade_history[-500:]
         return result
 
     def execute_multi_buy(
diff --git a/backend/core/world.py b/backend/core/world.py
index da2191f..93aa1e7 100644
--- a/backend/core/world.py
+++ b/backend/core/world.py
@@ -68,6 +68,9 @@ class World:
     step_in_day: int = 0
     time_of_day: TimeOfDay = TimeOfDay.DAY
 
+    # Agent index for O(1) lookups by ID
+    _agent_index: dict = field(default_factory=dict)
+
     # Statistics
     total_agents_spawned: int = 0
     total_agents_died: int = 0
@@ -87,6 +90,10 @@ class World:
         "clothes": 0,
     })
 
+    # Cached statistics (updated periodically for performance)
+    _cached_stats: Optional[dict] = field(default=None)
+    _stats_cache_turn: int = field(default=-1)
+
     def spawn_agent(
         self,
         name: Optional[str] = None,
@@ -154,6 +161,7 @@ class World:
         )
 
         self.agents.append(agent)
+        self._agent_index[agent.id] = agent  # Maintain index for O(1) lookups
         self.total_agents_spawned += 1
         return agent
 
@@ -327,11 +335,8 @@ class World:
         return inheritance_info
 
     def get_agent(self, agent_id: str) -> Optional[Agent]:
-        """Get an agent by ID."""
-        for agent in self.agents:
-            if agent.id == agent_id:
-                return agent
-        return None
+        """Get an agent by ID (O(1) lookup via index)."""
+        return self._agent_index.get(agent_id)
 
     def remove_dead_agents(self) -> list[Agent]:
         """Remove all dead agents from the world. Returns list of removed agents.
@@ -457,7 +462,23 @@ class World:
         return [a for a in self.agents if a.is_alive() and not a.is_corpse()]
 
     def get_statistics(self) -> dict:
-        """Get current world statistics including wealth distribution and demographics."""
+        """Get current world statistics including wealth distribution and demographics.
+
+        Uses caching based on performance config to avoid recalculating every turn.
+        """
+        from backend.config import get_config
+        perf_config = get_config().performance
+
+        # Check if we can use cached stats
+        if (self._cached_stats is not None and
+            self.current_turn - self._stats_cache_turn < perf_config.stats_update_interval):
+            # Update just the essential changing values
+            self._cached_stats["current_turn"] = self.current_turn
+            self._cached_stats["current_day"] = self.current_day
+            self._cached_stats["step_in_day"] = self.step_in_day
+            self._cached_stats["time_of_day"] = self.time_of_day.value
+            return self._cached_stats
+
         living = self.get_living_agents()
         total_money = sum(a.money for a in living)
 
@@ -491,11 +512,13 @@ class World:
             richest = moneys[-1] if moneys else 0
             poorest = moneys[0] if moneys else 0
 
-            # Gini coefficient for inequality (0 = perfect equality, 1 = max inequality)
+            # Gini coefficient - O(n) algorithm instead of O(n²)
+            # Uses sorted list: Gini = (2 * sum(i * x_i)) / (n * sum(x_i)) - (n + 1) / n
             n = len(moneys)
             if n > 1 and total_money > 0:
-                sum_of_diffs = sum(abs(m1 - m2) for m1 in moneys for m2 in moneys)
-                gini = sum_of_diffs / (2 * n * total_money)
+                weighted_sum = sum((i + 1) * m for i, m in enumerate(moneys))
+                gini = (2 * weighted_sum) / (n * total_money) - (n + 1) / n
+                gini = max(0.0, min(1.0, gini))  # Clamp to [0, 1]
             else:
                 gini = 0
         else:
@@ -538,6 +561,11 @@ class World:
             "village_storage": self.village_storage.copy(),
         }
 
+        # Cache the computed stats
+        self._cached_stats = stats
+        self._stats_cache_turn = self.current_turn
+        return stats
+
     def get_state_snapshot(self) -> dict:
         """Get a full snapshot of the world state for API."""
         return {
diff --git a/config.json b/config.json
index a9bfc09..0da74f7 100644
--- a/config.json
+++ b/config.json
@@ -1,8 +1,15 @@
 {
+  "performance": {
+    "logging_enabled": false,
+    "detailed_logging": false,
+    "log_flush_interval": 50,
+    "max_turn_logs": 100,
+    "stats_update_interval": 10
+  },
   "ai": {
-    "use_goap": true,
-    "goap_max_iterations": 50,
-    "goap_max_plan_depth": 3,
+    "use_goap": false,
+    "goap_max_iterations": 30,
+    "goap_max_plan_depth": 2,
     "reactive_fallback": true
   },
   "agent_stats": {