SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9a50a40a7bb76383f188ada56f71528ebfcd5aa5f6fd639729c89814cc44460' 
  AND token = 'fxEHoe9BMUWoJZzc7QGoOBSL78lphJKQVTNC/wl62LA=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00042

JSON explain

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