SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a06f255ec6445b8c4b362e1eb94cc4110bb2aac018192e9c8e312fa346483b49' 
  AND token = 'aKN2goqKSKowEH87Ji8OstE+axv4x56afODnUlDHKDY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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