Levels
What each level actually asks for
What each rung of the engineering ladder actually asks for, and which parts of it are learnable on purpose rather than by waiting.
From L5 to L7
The senior-to-staff jump, and why the subject matter moved into machine learning.
The jump from L5 to L7 is not more code. It is scope: L5 owns a service, L6 owns a problem across services, L7 owns which problem is worth solving. What has changed is the subject matter - an increasing share of the systems that judgement is applied to now have a model in them.
ReadThe L7 engineer
Senior staff: owning the bet rather than the design.
An L7 (senior staff) engineer owns a bet, not a system. The work is choosing which problem is worth solving across an organisation and being right often enough that the reasoning stops being questioned. Technical depth is assumed at this level; what distinguishes it is judgement under genuine ambiguity.
ReadThe L6 staff engineer
Staff: the first level where the blast radius is other teams.
An L6 (staff) engineer owns a problem that spans services rather than a single system. The design is judged on what it costs neighbouring teams and on which future options it closes off - so the step up from senior is largely about consequences beyond your own codebase.
ReadThe L5 senior engineer
Senior: trusted with the design, judged on whether it works.
An L5 (senior) engineer owns a service end to end - design, delivery and operation - and is judged on whether it works. It is the level at which supervision stops: the design is yours, and so is the outage.
ReadL6 vs L7
Staff and senior staff, and the one difference that matters.
L6 owns a problem; L7 owns which problem. A staff engineer is judged on the solution and what it costs neighbouring teams. A senior staff engineer is judged on having picked the right thing to solve at all - the design work is assumed. That is the whole difference, and it is why L7 is hard to study for.
ReadFAANG levels, explained
L3 to L8, what each one is judged on, and how the ladders map.
Google runs L3 (entry) to L8 (principal); Meta uses E3 to E8 and Amazon SDE I to Principal. The bands map loosely and the titles are not interchangeable. What is consistent is the axis: each rung widens the scope you own and shifts what is being judged, from whether the code works to whether the direction was right.
ReadThe L4 software engineer
The level where you are trusted to break the problem down yourself.
An L4 software engineer is given a problem rather than a task. The step up from entry level is not output but decomposition: deciding what the pieces are, in what order, and which of them is actually risky. The code is still reviewed; the plan increasingly is not.
ReadL5 vs L6
Senior and staff, and the thing that stops being enough.
L5 owns a service and is judged on whether it works. L6 owns a problem across services and is judged on what the solution costs the teams around it. The jump is not more code or bigger systems. It is that being locally right stops counting as being right.
ReadThe L8 principal engineer
Principal: the technical direction of an organisation, not of a project.
An L8 principal engineer is accountable for technical direction at the scale of an organisation rather than of a problem. The work is largely deciding what an entire area should be doing over years, and being the person whose read of a technology the company is willing to bet on.
ReadStaff vs principal
Two titles, several meanings, and how to tell which one you are being offered.
A staff engineer owns a problem that crosses teams; a principal engineer owns the technical direction of an organisation. The complication is that neither title is standardised - a principal engineer at a 200-person company is often doing what a large company calls staff, at a fraction of the scope.
ReadMeta levels, E3 to E8
The E ladder, what each band is judged on, and how it maps to Google's.
Meta runs E3 through E8 on the individual-contributor ladder: E3 entry, E4 mid, E5 senior, E6 staff, E7 senior staff, E8 principal. It maps onto Google's L3 to L8 more closely than any other large-company ladder, and E5 is the level Meta treats as terminal.
ReadAmazon levels, SDE I to Principal
Four bands where other companies use six, and what that compression hides.
Amazon runs SDE I, SDE II, SDE III and Principal on the individual-contributor ladder, commonly numbered L4 to L7. It compresses into four bands what Google spreads across six, so one Amazon level can span two elsewhere - which makes Amazon level conversions the least reliable of any pair.
ReadMicrosoft levels, 59 to 67
Numeric bands, two per title, and why 63 is the one that matters.
Microsoft uses numeric levels rather than named rungs: SDE around 59 to 60, SDE II around 61 to 62, Senior SDE around 63 to 64, and Principal around 65 to 67, with Partner and Distinguished bands above. Most titles span two numbers, so a promotion within one title is still a real step.
ReadApple levels, ICT2 to ICT6
Five bands, a hard ceiling at ICT4, and the least public ladder of the lot.
Apple's individual-contributor ladder runs ICT2 to ICT6: ICT2 entry, ICT3 mid, ICT4 senior, ICT5 staff or principal, ICT6 senior principal. ICT4 is the terminal level, and the step past it is reported as unusually hard - strong reviews at ICT4 do not reliably produce an ICT5 promotion.
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No course promotes anyone. Levels are awarded by employers against their own ladder, on evidence collected over months. What material like this can do is close a specific knowledge gap that is currently in the way.