SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a794290ded220976ef91bbc482f6d1021e54675f34bef2fc8b430f8736703198' 
  AND token = 'r7YtQ3I4Cc9T2P/frhD0vjvPt1NrBYtEvca8TQzIbOM=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

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