SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a42d2290a81124401f3587fbc262187416bac4192587ba759f7382cdfae86e45' 
  AND token = 'P96aZkE79418vMPRDvhm4bEdEF8h6IDeCnVbxutpxsw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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