SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '768525c4113a668ecba0ee660aa336bbe40da1a4f34a942694c299023687854f' 
  AND token = 'UMK0UZuy6aRtJwDMdOzz7E7qPyridLjDh2S+AoA4GtQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00051

JSON explain

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