SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '639167a2f3a3235a5e540d88c7e803c4b1d3e8329baf8834b69781292a5e2f91' 
  AND token = '24+CNMGaKUpjEQZLbrgLENXbapT8hEry+kk/DB+tcIE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00032

JSON explain

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