SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '2b7db21335b614de84e02282c196caec556386688b19364201839a59bde63c34' 
  AND token = 'JHK2EorfVEkmHyiKlubuB66oHj5ZmFXf/U7jizJ13Gk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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