SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'cf6ad867023f075f50a3a14114792b0dd2ee13ab112fec521e5e8d95751c7e31' 
  AND token = '3i9Xgy/Mx+N2uvyc8oDJdyO2twrEtoy5+zRWtW28zvs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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