SELECT 
  1 
FROM 
  cscart_aprillock_keys 
WHERE 
  key_id = 'a6d34256cd0582d6671d14624be3928189e73450d66a497b1783f7afa6978b53' 
  AND token = 'DMODIMrUisPVL2LR3caImYeFZX4TeGwwJvLQhUdVmLU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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