SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '50dea8105e491de8806ce27647e3aa5b30ae4aadd9554e0d92990eb30acdebcf' 
  AND token = 'WiM+fzYDPMuclyK3sWY0b/Kw6HUyZ8eBuhNuM037yN4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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