SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '83e435636206af43dfa2bef0b31da0b98069487f3578018f3a8dbe05d5d91fa8' 
  AND token = 'F0MdbH8UPFJojPl006cgjfdrFwjqPJdZYhrXmb/DWNg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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