SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b7af8650219311f22b580e0585da6c911bbd0404e880d787215eceb52a11f6fe' 
  AND token = 'R2q/xNUQgRge0Px8lUWpTAKh2Xw/7VP3NwjYE/gvGm8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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