SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '851d249854288e3d8f300ef25247a17ad7dfc9e2e5dcaa63a35ce56261c24082' 
  AND token = 'FLOFLX1LEwbSibSp3tL4H2DJ7sT2/CfrmMmeAKMvJ+4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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