SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6f15d27a7b01efc96719e81acad1f53c0b901c3af16bc5fc2c310ab376269fb3' 
  AND token = 'kL3SBlg4N4mjjKzdV6mFB2lzkXpqATgnnRutXjKYokE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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