SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'af8a16bc05d0894c32b37d073c4d1e954d18dc5cd387c3d00832756adcc7d8ae' 
  AND token = 'QMu2aGRnAwAaQx0PE9wdEBUzZ2awsffMaiy0S/JGkn4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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