SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b4d3210a4768076a90c7508b719554466cbfe450a16917d687e5750d88f3fccd' 
  AND token = 'I98vKg5+G9oabpxlqyxBJxvNOvr6w6ucXmUfnJs0GZw=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00027

JSON explain

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