SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '6a6d62c30f9fa891f8d2680ae48166f4379886a3034c2341a4517734234632df' 
  AND token = 'Lr3JAurXgmCBPyB5rClPicXiVEtT3laKDOaBMRTjgAw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00025

JSON explain

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