SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c21b68a08303c139743f9d8587e4b178efdbc66b7648de61bc50a463421211a9' 
  AND token = 'SIDpcjqHqmY5nDhI3Ws36J1/xzgytnGom5vZWmqQO/Y=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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