SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b58ee453b68fb7839e7b9b519fdbf4eb68349ce25cc3e58c2a6df016a3168438' 
  AND token = 'UIWLeE9nasZLqFPwfmTWmY0ChdPnVKVzcCowSJTpBTY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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