SELECT 
  1 
FROM 
  cscart_multi_declock_keys 
WHERE 
  key_id = '6ba23199162be223d81066645965a0796103a96e6c208f0bc39b94a6cb847a57' 
  AND token = 'p0Bhn4wAPacHH8XPJ+/QXIu0PZIUVdeF2VI2lTKgJp0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00017

JSON explain

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