SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '52a766d28abf7beee0e2488cfb3c42e4544cf8cc6e9c9d5d5ee82c5e449608ac' 
  AND token = 'QsXDkpVo1YerrJ+krF3tEvbfhIgUGvPGBcPh64F8sHk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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