SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '44d5b12db1539843426e2d8257e8d055381b45fb0689d67a3fbe3bc20dc7cb51' 
  AND token = 'W4zm91t/fRjXvEvkL+YANEoeseF4Tdul7IZbcsVT0/A=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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