SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6ef0019c99dbb97464d0b8417f71c4b8051859839e22b4f0a63434939f37987f' 
  AND token = 'rsg4LMjPj12EBJCzFsOvpWfPchbC+iY/avpfxVBJm5k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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