SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cb90909d232a718e45587fcc65446558ca1df7cbc1f0643329f108a9ca99fb52' 
  AND token = 'z6KifRVj9EYQF+ZDWtkgmAK3AEPlMT/LE1h+wJRx++0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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