SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '35e3ece64fec52c462366e96609517afa4f527035dd58318adb84e0d7f37ced6' 
  AND token = 'nnEM2IF3GoAEXLru5mgBW+atpEv0flQ4yS54Rn3Krfk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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