Technical Skills and Tools Questions

# Use a small official Python runtime
FROM python:3.11-slim

# Set working directory
WORKDIR /app

# Install build dependencies, then remove caches in same layer
RUN apt-get update && apt-get install -y --no-install-recommends \
    build-essential \
  && rm -rf /var/lib/apt/lists/*

# Copy requirements and install (pip cache disabled)
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy application source
COPY app.py .

# Create non-root user and set ownership (best practice)
RUN useradd --create-home --shell /bin/bash appuser \
  && chown -R appuser:appuser /app

USER appuser

# Expose port and run app (use production server in real apps)
EXPOSE 5000
CMD ["python", "app.py"]

-- Postgres example
SELECT blocked.pid AS blocked_pid, blocking.pid AS blocking_pid,
       blocked.query AS blocked_query, blocking.query AS blocking_query,
       now()-pg_stat_activity.query_start AS duration
FROM pg_locks blocked_l
JOIN pg_stat_activity blocked ON blocked.pid = blocked_l.pid
JOIN pg_locks blocking_l ON blocking_l.locktype = blocked_l.locktype
  AND blocking_l.database IS NOT DISTINCT FROM blocked_l.database
  AND blocking_l.relation IS NOT DISTINCT FROM blocked_l.relation
JOIN pg_stat_activity blocking ON blocking.pid = blocking_l.pid
WHERE NOT blocked_l.granted AND blocking_l.granted;