SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a9f51b74062bdabf79a530813e32653a4fdd8967bf7bc0f6226403de119932fb' 
  AND token = 'op3Ol9DpAtNzSLXtUUIFNPA6MLj+IXS0pGrHfD9n4Dg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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