SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '57646d630473a321811f179f4e2f29c49ba627fdc391ad50864090944ac905b6' 
  AND token = 'JrVEDmjO3tXiMnp58FSlFji/PKDnM3dZKHazZytH65k=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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