SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'e6c4a2168ece720f67e2e2553a0bca88540b2aace42752c3b789b1f498276ddb' 
  AND token = 'n0fGWJ70ySM5SiFGV98pi28EtR7Ipm1tDaLznsFDqBk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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