SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '126844a00701669980835fd3b8e1ecf377a50d4a19661255a36e636f76c25729' 
  AND token = '0mYqugNJYxl7KrwhNw1guLUcPCGXC3OLCsvcVJbaaus=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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