SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '51376ad398b9a2736e3df246c6d96e2686e70d699edfcacb28716c0b76ce1c70' 
  AND token = 'odl18riuIVrxf7in1m5b8EiyXpfwZwUiEcX0vWAl9ds=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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