SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21e2677603ce90893b4b671c6e2840d3bad4fa6721fb25720a863bf5c609f236' 
  AND token = 'fJ3zwJkzhGy4Q1rqSKxjOdndOhuxVvnh694WLKxZxko=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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