SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'c5761a09ca46dcac9082ec0f16a78b45bfe209bb23dcbca1e5c1d861fe9a4002' 
  AND token = 'lThaS3uqPxuh/rmVWZCTBlVVrL5cM/EfGsXQp7GaNgM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00020

JSON explain

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