SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5297098561ecd6387a576e753b16c33a0d20d733b093bf0a9fcba283cab029ff' 
  AND token = 'dEDOEPRkpVyT69m4YhuT+vR4NAr1daM1mLyaT78+/so=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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