SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '8cdf38e00d28259058d2873c952d689782e134741719a209750dd78cb617cbd1' 
  AND token = 'yj3kF3u/NLS1SRaKanOl3XPW/qn7NQzjGa5yRZhBgO0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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