SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c8df528b70b35bf17217965126847b30bbeb431c0516b53bd4c2ab619be1d560' 
  AND token = 'FiCJzVBzhySyzKd+rw7RGggtI1zGxukadLIYQ2WMLB4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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