SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6dfaa2223b8bc828fe035f8b1b6fd0d0733d2d3a249f0b3138ff2e6d9ef7576f' 
  AND token = 'H/FNrmq4Sl9hS06AGcVorOy9uz9UvGlDynvBIPdAwYs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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