Summary
Sell-side infrastructure modernization is critical for investment banks constrained by legacy systems and fragmented data. Aging architectures limit scalability, delay product launches, and hinder real-time transparency. A unified operating platform enables efficient growth, supports complex products, improves client experience, and unlocks intraday intelligence across global, multi-asset operations.
Big sell-side players are trying to break free from their investment bank legacy systems and fragmented data environments, which limit their ability to scale into new markets, onboard new products, and meet rising client expectations. In fact, two-thirds of US and UK banking leaders estimate that their systems’ oldest operating programming code was written prior to 2000, and 30% estimate their oldest technology infrastructure to be from the 1960s or earlier.i Enterprise systems are often built by retail banking units for credit cards or auto loans and are not purpose-built for complex institutional tasks like financing equities on swaps or structured products. For every drawback of legacy technology that sell-side leaders can see and quantify, there are other, less visible drawbacks that erode margins and bog down workflows.
Fragmented environments often force firms to run separate, redundant middle-office functions for different strategies, resulting in a revenue-hemorrhaging exercise. Most sell-side leaders have endeavored to revamp operational and data technology, at least to some degree, but also to varying levels of success. Aging platforms continue to handle valid banking operations but have become invisible ceilings that stifle efficiency, block revenue growth, deter talent acquisition, and create systemic risks.
Here are some of the less visible barriers to efficiency and growth, and why now is the time for institutions to revamp key banking systems.
As the industry reacts to ongoing structural change, investment banks have found the biggest symptoms — errors, inefficiency, and complexity — causing their biggest disease: They can’t grow. Brilliant financial minds are writing checks their systems just can’t cash. Workflows are accelerating across the board. Our attempts at marrying high-velocity digital transactions with aging infrastructure are...a marriage on the rocks.
A primary mechanism for funding trillion-dollar balance sheets, repo markets are shifting from bilateral to cleared structures. A single economic trade can generate dozens of clearing trades, dramatically increasing market data volume as well as anomalies. It is critical for banks to have modernized data models that can handle the surge without manual workarounds. Systems built to deal with static trades and end-of-day processing buckle under flows of new cleared repo business with many more events for each trade.
Global expansion requires managing data across multiple jurisdictions with differing rules for data masking and regulatory oversight. Big banks that have enjoyed acquisition-led growth find themselves operating a trillion-dollar global balance sheet across 80 different markets, creating the need for a unified operating platform to consolidate what had become a deeply fractured infrastructure. Meanwhile, a treasurer funding that trillion-dollar balance sheet might receive 20 different middle-office and risk reports. Most of these are delivered only once per day, making real-time capital allocation nearly impossible without modernized infrastructure.
Economic asset reference data like interest rate, inflation, and consumer pricing indices are necessary to monitor interest rate volatility, allowing the bank to track inflation and reposition strategies as desired. Bank systems must have the bitemporal modeling capability to track both effective date and knowledge date time horizons, thus enabling the linkage of changing analysis outputs to their economic drivers.
“Technology followed business into silos. Each line of business built its own stack, its own data model, and its own client lens. That model worked when innovation meant better channels, but not when growth depends on connected experiences and integrated advice... Meeting this challenge requires more than incremental fixes. It demands re-engineering—creating the data, governance, and delivery models that can connect business lines and their technology foundations. This is not about centralizing control; it’s about building connective tissue across an increasingly federated organization. Banks that learn to work horizontally can move faster, serve customers better, and unlock growth capacity others cannot.” — PwC, Re-Engineering the bank for growthv
Older capital markets’ operational infrastructures are impediments to growth and grossly inefficient, as well as inadequate in supporting complex financial products. Many senior investment bank leaders are facing the realization that the systems that have been churning along for two, three, or four decades are not going to be the systems driving the next 10, 15, or even 20 years of growth and change.
Legacy systems are frequently built on different codes and closed environments that prevent them from working together. Consequently, when a bank wants to launch a new product or asset class, it must build standalone infrastructure rather than plug into a scalable platform, leading to further complexity. Throughout the digital transformation, the industry advanced through channel innovations and through the digitization of treasury, cash management, and electronic trading in corporate and capital markets businesses.vi Core systems have been largely untouched until recently. This phase of digital transformation calls for banks to look at data modernization through an organizational lens, so they can launch and scale new product lines.
The combination of various underlying assets such as loans, mortgages, and receivables into tradable instruments are increasingly instrumental to bank strategies for regaining market share from private credit and optimizing their balance sheets. Asset-backed securities, mortgage-backed securities, and significant risk transfers challenge Swiss cheese enterprise architecture, which lacks the specialized data models needed for the hundreds of unique attributes needed for swaps or complex loans. Modern structured products often involve sticky transactions ranging from $10 billion to $30 billion. Banks need the ability to do intraday funding to cope with the constant volatility in bank balance sheets. This type of balance sheet optimization in funding a bank’s trading book in the most dynamic, opportunistic manner doesn’t happen without a unified operating platform that serves up real-time collateral inventory and valuation data.
When a client inquires about a settlement break, an operations professional in a fragmented environment must often call three different desks just to gather basic intelligence. In contrast, modernized firms use AI and unified data layers to resolve issues in minutes, providing a white glove experience that legacy systems cannot replicate. Large institutional clients, who often pay between $10 million and $100 million in annual fees, are increasingly unwilling to accept the limitations of legacy systems that provide information only once per day.
Clients are operating with shortened settlement cycles and asking for true intraday P&L — including all accruals for financing, audits, legal fees, and management or incentive fees — rather than flash P&L. Some buy-side firms expect an Amazon-like experience for their standing settlement instructions (SSIs), asking bank systems to automatically apply SSIs and facilitate repeat functionality when trading securities. In short, sell-side clients expect tailored business insights and responsiveness to their own evolving business models.
As sell-side institutions embark on their infrastructure modernization journeys, they will find they are able to swiftly onboard new clients, product lines, or tradeable assets like crypto, structured products, or private markets vehicles. Their newly unified operating infrastructure — a centralized data foundation working in concert with a front-to-back operations platform — will handle booking, risk, compliance, and reporting seamlessly as institutions bring in new business and greater data volumes.
Systems modernization delivers operational efficiency gains of 20%–35%, increased revenue from faster speed-to-market, and 20%–40% cost savings from sunsetting legacy systems and the associated upkeep and upgrade costs.vii Translation: pure competitive edge.
Ted O’Connor
Ted is a Senior Vice President focused on Business Development at Arcesium. In this role, Ted works with leading financial institutions in the capital markets to optimize data, technology, and operational needs.
Sources:
[i] Baringa via Globe News Wire, September 16, 2025. https://www.globenewswire.com/news-release/2025/09/16/3151199/0/en/Baringa-Survey-Finds-that-Legacy-Tech-Infrastructure-Remains-a-Challenge-for-Banks-as-Demand-for-Digital-Banking-Grows.html
[ii] Financial Markets Standards Board Limited (FMSB), May 2025. https://fmsb.com/wp-content/uploads/2025/05/Uncleared-Margin-Spotlight-Review_May-2025_FINAL.pdf
[iii] BCG, 2019. https://www.bcg.com/publications/2019/creating-digital-treasury-banking
[iv] BCG, October 14, 2025. https://www.bcg.com/publications/2025/driving-growth-in-corporate-and-investment-banking
[v] PwC, November 18, 2025. https://www.pwc.com/us/en/industries/financial-services/library/re-engineering-the-bank-for-growth.html
[vi] PwC, November 2025. https://www.pwc.com/us/en/industries/financial-services/library/re-engineering-the-bank-for-growth.html
[vii] EY, May 2024. https://www.ey.com/en_us/industries/financial-services/five-rules-of-core-modernization-success
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