SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '753846816c3f5ade44c291e4883916dfe2753b6a08f58d74260110be49d910df' 
  AND token = 'FVvwV6bKBaDIlXuw7XokSXW2IeFWS2jvTD1NxBQmvR4=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00023

JSON explain

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