SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd151220f15d1b93573e2363acab55d68fd949ac77980485688ad66a60af4e4da' 
  AND token = 'zuVfQjXdLs5amQNyt1p10McnHiIQWiySuamzupfFnkI=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00031

JSON explain

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