SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '82a76c2352b074e687591e40727d726f5f33c84e008bf659029003c90296a51f' 
  AND token = 'RvdO9NubaMB/RoShIytiFJNQzYChFSBHaoSUlZrMR70=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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