EventStats lambda with Stats endpoint (#113)

Author: tmikula-dev

.github/agents/devops-engineer.agent.md

@@ -4,27 +4,34 @@ Purpose
 AWS Lambda event gateway that receives messages via API Gateway and dispatches them to Kafka, EventBridge, and PostgreSQL.
 
 Structure
-- Entry point: `src/event_gate_lambda.py`
-- Handlers: `src/handlers/` (HandlerApi, HandlerToken, HandlerTopic, HandlerHealth)
+- Main lambda (event ingestion): `src/event_gate_lambda.py`
+- Stats lambda (read-only queries): `src/event_stats_lambda.py`
+- Shared config loading: `src/utils/config_loader.py`
+- Handlers: `src/handlers/` (HandlerApi, HandlerToken, HandlerTopic, HandlerHealth, HandlerStats)
 - Writers: `src/writers/` (inherit from `Writer` base class)
+- Readers: `src/readers/` (read-only database access for stats)
 - Config: `conf/config.json`, `conf/access.json`, `conf/topic_schemas/*.json`
 - Production Terraform scripts are not part of this repository; `terraform_examples/` for reference configurations only
 
 Python style
 - Python 3.13
 - Type hints for public functions and classes
+- Use built-in generics for type hints
 - Use `logging.getLogger(__name__)`, not print
 - Lazy % formatting in logging: `logger.info("msg %s", var)`
 - F-strings in exceptions: `raise ValueError(f"Error {var}")`
 - All imports at top of file (never inside functions)
 - Apache 2.0 license header in every .py file (including `__init__.py`)
 - Docstrings must start with a short summary line
+- No blank lines between docstring sections (summary, Args, Returns, Raises)
+- Use single backticks in docstrings (`value`), never double backticks (`` ``value`` ``)
+- Do not use `# -----------` separator comments to divide sections
 - End all log messages with a period: `logger.info("Message.")`
 
 Patterns
 - `__init__` methods must not raise exceptions; defer validation and connection to first use (lazy init)
 - Writers: inherit from `Writer(ABC)`, implement `write(topic, message) -> (bool, str|None)` and `check_health() -> (bool, str)`
-- Route dispatch via `ROUTE_MAP` dict mapping routes to handler functions in `event_gate_lambda.py`
+- Route dispatch via `ROUTE_MAP` dict mapping routes to handler functions in `event_gate_lambda.py` and `event_stats_lambda.py`
 - Separate business logic from environment access (env vars, file I/O, network calls)
 - No duplicate validation; centralize parsing in one layer where practical
 - Preserve existing formatting and conventions
@@ -33,14 +40,13 @@ Patterns
 
 Testing
 - Mirror src structure: `src/handlers/` -> `tests/unit/handlers/`
+- Test modules (`test_*.py`) must not have module-level docstrings
 - Unit tests: mock external services via `conftest.py` (Kafka, EventBridge, PostgreSQL, S3)
 - Integration tests: call `lambda_handler` directly with real containers (testcontainers-python for Kafka, PostgreSQL, LocalStack)
 - No real API/DB calls in unit tests
 - Use `mocker.patch("module.dependency")` or `mocker.patch.object(Class, "method")`
 - Assert pattern: `assert expected == actual`
 
 Quality gates (run after changes, fix only if below threshold)
-- black .
-- mypy .
-- pylint $(git ls-files '*.py') >= 9.5
-- pytest tests/ >= 80% coverage
+- Run all quality gates at once: `make qa`
+- Once a quality gate passes, do not re-run it in different scenarios