SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'b39802237e178c0b9a4ce8ebbe26565eeaa7753b82ae7f9262e86bd4b5db1a1c' 
  AND token = 'GyxVa1EAFtnTpBrQxTp0u9Wjy/72b/13t5/kHdzLCnY=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

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