SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '68e51d6942bc7dd2a2d9b971dfc298a9516a766d64cd047ed7c92372dd701823' 
  AND token = 'QyOlcdRDmtJJPahPPwwRnovuymSrSuxDfWMy0yxEo6s=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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