SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '291ddc3b2df40dd79084555aa43045261fa1a4560b65abc1480a5ebce9a45a83' 
  AND token = 'Qlq6Euxrzf2HcNId8305u6ZgiZ764OVXllXh8WUi/m8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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