SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c9a961d14f96f61c357d1d1fa51907a4d4ad59771f34d38032d67bb936033e39' 
  AND token = 'iSgfDSNMOpDUHjoSo+1CJjJi4mu16fWWjcm50pZKd5k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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