SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '975c76600f3c28642fe9e011990dc6e549912036ef9949a21c5c18827fb229b2' 
  AND token = 'uUolbbBlll8cUF1EcxC63O8v34T85kc06yMTdIzSVdo=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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