SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b78fb7314b636358999681725be6993a251fb81ef1e88e819edfc17e442f6315' 
  AND token = 'D4+b2LBgIC31RDKKaI2He37PXy+2mJd+4loKla3Eplo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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