SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '12c3850a354bdbe335130e948041fc3c2ad4856063a5352b312b81dd756b5c72' 
  AND token = '4JlamfmnUiInFHEMEFvoYVAJ2ArXQWT/nrRRgFXPMaI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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