SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b84f66e218ebe5f8de8b1834d0d4d075f44d6e6d44ee4043e69bc664d354c0a7' 
  AND token = '992yUhZBnoH1iCgdzF1UMJZTUJXfeFmYTvhzujRIr5o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00053

JSON explain

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