SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7ff375aee406480c69033218735afe724c28b08cc9d712239855365a29c232d0' 
  AND token = 'YJR5fdZqTp+KnnHFoCpG6ttsJ0xfpm/iHlUHdDZDvJw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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