SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '71e7dd53e49fb96e714355f64faba42c839a7c656364fcb91d95617704593738' 
  AND token = '9vs3AYERJm+aO5KMgFTqmcBGKx1rfvu+kkY/lGQ5p9s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00030

JSON explain

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