SELECT 
  1 
FROM 
  cscart_june_setuplock_keys 
WHERE 
  key_id = '515b2494f57df8494936128b65b4e69d2accade94b73968617824057e27e0c96' 
  AND token = 'P1CRNroze7SBV6u+Gb+nDqqV/fzg7TWpX8bA7R+orNk=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00026

JSON explain

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