SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b29375f6e188350c8f5bdcebf62da94680016303d3fce1796fa8ad47ab9d2332' 
  AND token = 'RdzJy7wM6K15AT0WFoMBvGtUsitybBfiqPhzAevavl0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00039

JSON explain

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