Exponential Backoff

The Schedule

 retry delays grow geometrically:

 attempt 1 fails → wait 100ms   → attempt 2
 attempt 2 fails → wait 200ms   → attempt 3
 attempt 3 fails → wait 400ms   → attempt 4
 attempt 4 fails → wait 800ms   → give up (cap reached)

 delay = base × 2^(attempt-1), capped at max:
     min(base * 2^n, max_delay)

 base ~100ms typical; max ~10–60s depending on operation class.

Why Growth Is the Point

 a struggling dependency needs TIME to recover —
 recovery means draining queues, GC settling, autoscaling.

 linear/eager retries hammer it during exactly that window:

 fixed 100ms retries:      10 req/s sustained pressure ✗
 exponential:              pressure DECAYS as failure persists ✓

 it's automatic load-shaping: the sicker the target,
 the slower the requests arrive. recovery becomes possible.

 second purpose: OUTLIER tolerance. transient blips resolve
 in ms; deeper trouble resolves in seconds. the growing
 schedule spans both without human tuning.

Jitter: The Non-Negotiable Companion

 synchronized clients retry on the SAME schedule:

 t=0:    dependency hiccups. 1000 clients fail together.
 t=100:  all 1000 retry TOGETHER → spike → fail together
 t=300:  all 1000 again...
 
 the THUNDERING HERD — your retry logic DDoSing its own target.

 JITTER randomizes each client's delay:
   delay = random(0, min(cap, base × 2^n))
   (full jitter) or ±50% around computed value (equal/partial)

 result: retry load spreads smoothly instead of pulsing.
 AWS-style guidance: full jitter performs best empirically.

Parameters That Matter

Parameter	Typical	Notes
base	100–500ms	below p99 of normal latency
factor	2	rarely tuned elsewhere
max delay	5–60s	bounded patience
max attempts	3–6	total envelope matters more
deadline	per-operation	attempts must FIT inside

 interactive paths: fewer attempts, tighter cap
   (user is waiting!)
 background/queues: more attempts, generous caps,
   plus DLQ at the end of the road.

Interview Framing

“Batch job hammering an API gets throttled, retries make it worse” scored diagnosis: missing backoff+jitter, prescribe exponential-with-full-jitter with concrete numbers, fit-to-deadline arithmetic, note the decay-pressure property as WHY it works. Two words interviewers listen for: “geometric” and “jitter” — say both, explain the herd once, move on.