SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '79ab746813274e644be3430b4fc01137547465b1f871bb862da80e71af9de3e0' 
  AND token = 'kx3iLmVH+YPmfQmf8Ygkqm/SOk/5AHbmJVAdTxOO888=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00019

JSON explain

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