Pros
Genuinely large-scale engineering problems — payments infrastructure at this firm handles volumes few companies in the world see, and you get real ownership of systems that matter. Benefits are excellent, especially the medical coverage. Work-life balance in engineering is reasonable and predictable, and job stability is far better than in tech. Opportunity to take on scope (tech lead, platform ownership) comes earlier than you'd expect. The brand carries weight everywhere, particularly in fintech.
Cons
Compensation lags the tech market significantly for equivalent engineering skill — expect a real discount vs. FAANG or fintech unicorns. Internal tooling and release processes can be manual and dated; a lot of engineering energy goes into coordination that modern CI/CD would eliminate. Career ladders push strong ICs toward management/lead tracks whether or not that's what they want. Pace of modernization varies enormously by team.