SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a709ec200d4ad6ab01d239d0490d064d629192761af7595da1a1edf786f5ca04' 
  AND token = 'AgrOw1iT5iHYqJzwNASJXieBQc8eVYfpBlUkGh+kxO8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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