SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a103d983fd7f94932ef56eea931138b3cc06c1da991910c300219c0459fce676' 
  AND token = 'hSJAWnvSPbYYXxy4NtlYaw4pO7rfyLO5SdTd2N90etU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00028

JSON explain

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