SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a6b1c7bdea9d9d739d66d193b5382904d06ee552535739d6e05098a86a82b317' 
  AND token = 'QsX59oSM0dkQDj86dX+hvREWrdYQufuIU7ADZKKNYQk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00035

JSON explain

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