SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '3fcf883e7ec0f94af7b523a99496414a72d2f370aeb4852f858e381a609cab2f' 
  AND token = 'S+Bx/kvu+sGR8RPwAGA0BUS7yb0sRdqC30gRCAjjqJQ=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

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