SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = 'b846abdfd07b1d3e424c72f8a13f2500642409398a466443b68cb46e42157bc3' 
  AND token = 'n3a3r67Qqazh468/x48hGvCdu/5qkXVDMdoXEkgim5o=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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