SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3f9b6436578e714234edfc956f215292c997d1ded2849067c238f4e01df98c5c' 
  AND token = '/oNMBzPjFlugEgY08GVp/Os/qiFq6DUrvF/sRc4qXYg=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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