SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '768629f33523bdded526665b80e25aca697c6e6687242df2167098707dd0bfe8' 
  AND token = 'jOcs2F0H8DOGZqWoNo1kpvthQltUweRAQVr2wM3sRGw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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