SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '52439b20bf89990ca306ec77cf0387eab6af9794bf9e8afb795a87840a1df051' 
  AND token = 'AhGfZPFWRd7BzLeCgcM3TM5/0HUp4PzeSVBpjvPOko8=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00041

JSON explain

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