SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b575a159c0d17264c7e9035d14097453d400530b62a95350fca72d0f8af0b0c8' 
  AND token = 'nU1Sva4FS3qOKO0YhZMY8SCw510hQgzJhRDtzfbePO8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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