SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '91384bb33af92e319954862af2f05c2af18cb90e68873fa06ea2a8e4bd847429' 
  AND token = 'v57v0nJjyum0az06RmjNBV/EDBWsKOg7+ehJPOhgXvY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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