SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'a3c9f21f4894b58e152c1dab3f823739d02a5b8c0460ce08c5788445429a70a2' 
  AND token = 'Si3KympvFI47AJRo8boZtMHSjohayDlaJtd4nhTjqWE=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00029

JSON explain

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