SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c3146d260570282dcc4d9b26415f07b9e68fac4c15cbab3dedac9e04af13112b' 
  AND token = 'GPeMino2JlScitOVvODl3zaKZpxzPmuLUbtBrelnWzk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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