SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '5c5a3a11ea05e832074cce4fac8843d2250f5711e43395dc9e91bb34eb97114a' 
  AND token = 'mZhmhAf3TqZZjSTpCx5MvxdkffWKxqH71s7UrfwMbsQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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