SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '0503404911c99a48b43aa3648b488f508b7a39a3b76c166013a535c44261c582' 
  AND token = 'p7sXZxAgh8H3g2FkC4gxf4LTBYZIdxATOovjYF5qcFU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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