SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '026b301ede682b05e6b311902cd7dbea51f79720d2da41c2be3665566478af98' 
  AND token = 'bZzsH1444j+FPuG3eu6pdP3yVjOn4TPC/uwdhR5RfGY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}