SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '811f27c9edd02421d61ed935dd25310fa10ecbc19e65395cb7dd44a4b19cd579' 
  AND token = '/onGtYKEUEwZczVSeYAixMFbaawOSJNCXdj+u15NpPo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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