SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '21ffea7ff9d86e5231e22eb2cc024dafe7d6f7196534f3dae22e9579612af1f0' 
  AND token = 'A6ihSHm22dmG6meuTZIkAvcpmOelCNWaAeTtxRXRg5Q=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00037

JSON explain

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