SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c820bff73fa06bd772bb27ac4932fc3b19b96b3180e7da4ee80642b8262c35db' 
  AND token = 'x1p8mdR1FxW7q7+K2wkX5tQJg62FsAdtOdOeyuY8Llk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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