SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b32296400d00a91a3e107b9a7b25b50880821c0577021c1a0798d465c7ac312' 
  AND token = 'aSgbRv3an6SbEwM4B3mjl0PVWnvPLrMa76QdHRebTDE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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