SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21670de11f5ba84ff4b33ba0840c8b3302352a44efd09b9416a82daafaca110b' 
  AND token = 'BU6WWXmxRoe2VPLYOJL3cy3iZ7ROXnnR63nAQfqn830=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00033

JSON explain

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