SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b8c26a0cad4c15fd60f707da298edbe390bd45315f205cdb88faa826450bb36f' 
  AND token = 'l46yDETOMqMG+R0Ews1jT4bYxJzZgb0NMeR91+hQK9g=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}