Proctor LEVEL-1VIVA-1

Simplecommit changes save. rollback fail pe undo. Transaction consistency ke liye.

Example

try:
    db.session.add(obj)
    db.session.commit()
except Exception:
    db.session.rollback()
    raise

SimpleDemo script pehle se practice: 5–7 min, Admin + User roles, saare mandatory features.

Suggested flow1) Register/login user
2) Admin login — CRUD
3) Approval/blacklist
4) Booking/apply + edge case
5) Search
6) Logout

Viva tipBolte-bolte dikhao. Code tab kholna jab poochhein.

SimpleMAD1 frontend usually Jinja templates + HTML/CSS/Bootstrap (+ thoda JS). MAD2 pe Vue ho to clearly bolo.

SimpleCache = pehli baar hisaab karke copy rakh lo, doosri baar copy dikha do.

Baar-baar same expensive kaam (DB query, counting bookings) mat karo. Result Redis jaise store mein timeout ke saath rakh do.

Cache hit: key mil gayi, DB skip. Cache miss: DB se lao, SET karo, return karo.

Tradeoff: speed vs stale data. Admin naya venue add kare aur cache 50s ka ho to user purani list dekh sakta hai — isliye write pe invalidation zaroori hai.

Browser cache, Flask-Caching, Redis alag layers hain. MAD2 examiner Redis + @cache.cached code dekhta hai.

Example

@cache.cached(timeout=50, query_string=True)
@app.route('/api/shows')
def shows():
    return jsonify([s.serialize() for s in Show.query.all()])

Project example: Admin dashboard counts / venues list cache. Create/update/delete ke baad cache.delete('venues').

Viva tipprint('DB queried') function ke andar laga ke miss/hit demo karo — hit pe print nahi chalega.

SimpleRedis box hai, Celery us box se kaam uthane wala worker hai — same cheez nahi.

Redis: store (cache keys) + queue (broker lists).
Celery: Python library jo tasks define karti hai, .delay() se queue mein daalti hai, worker execute karta hai.

Dono localhost pe ho sakte hain. Alag Redis DB index use karo. Redis band = cache miss + Celery stuck.

Example

Celery: broker_url='redis://localhost:6379/0'
Cache:  CACHE_REDIS_URL='redis://localhost:6379/1'

Project example: export_csv.delay(user_id) Flask se. Worker Redis se task uthata hai, CSV+email. Cache alag keys venues.

Viva tipAgar possible ho to cache db=1, broker db=0 — keys mix nahi hoti.