SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '759e8a8b866099490ec5448093d22b0f0c5749dcc70d671e8677ca4c906667f9' 
  AND token = '40jnDbAoHpjQBR+7dzfasaSwECeoPhzEiKes8238PXY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00043

JSON explain

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