SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a4ec5e91b781fea71d692f8b4a5368f4bbd4707c8f920583a02d0d53fc92e6fe' 
  AND token = 'C2k1lSPz2IJaqX0dZYB1jvOmZRl+Jrug03xNGJeXif4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00058

JSON explain

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