SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '855df83a26d6539708ea56917344ea52cfb0531217410311c872b0ca5399e701' 
  AND token = 'MJvGJHeUuUNeJqjmygiWtNse/ckoUr5YOJgEAMEMftI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00016

JSON explain

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