SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b82ddf939ba4b8285b9fffd12d06680fa942b755677f3644e6482ade47a458ad' 
  AND token = 'lP0pmhePNTwABAByOqntIQwKJeiCHKW8exrv+XLAf0g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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