SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b6c1b1c1af1367c9e04e51b7e32fe0c1e3ed2f207aa269691604d15fc54b84d1' 
  AND token = 'ERLrekg0gsed0xPcTUVT9AZ+sJLJDClg1+ifsjtHEb0=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00024

JSON explain

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