SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb935bda7a5ffe9fb0786156cd7b4afa751d7eb9bf869506cc592f003df7b4bf' 
  AND token = '6HVfdaaiCE+LA7+q9ngWrJMQbj2lsWmmYvdjR0vfmuk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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