SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b83a09b38e8458d8df61fcb0067e5e586407d8b02da861458bb249ee24e01d81' 
  AND token = 'RHxk8mL0rxLI1N3maZj00XSJExC8kI7rdiDwZewgGrI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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