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SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '664a0b79e4a53f0a0ee8df2ee3f028c292434a941d603c6d7cef4f50cb5daf0c' 
  AND token = '/AYYTYEejLSnYzmiv0Lo+uWJkM8GK4JjPOMRu/tJTEI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00021

JSON explain

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