SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3b4e81881eca6956698b80138c0fdc1c23300e533e6a0c6845d2763c689d5d1b' 
  AND token = '76ykM4oN/bFVG9rwwUd4O3/oLk24sJN0HNPRpzPg+hk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

{
  "query_block": {
    "select_id": 1,
    "table": {
      "message": "Impossible WHERE noticed after reading const tables"
    }
  }
}